-
Solution 1
The numerator is equal to . The denominator is equal to
, so
Solution 2
By factoring out of both the numerator and denominator, we get
Answer: 3
-
Solution 1
Solving for , we have , so
Solution 2
By factoring and substituting, we get
Answer: 2
-
Solution 1
From the information given, is the reflection in the -axis of
and is the reflection in the
-axis of . Since the coordinates of
are , this means the coordinates of
are . Similarly, since the coordinates of
are , the coordinates of
are .
The slope of segment is . The slope of
is , so the sum of the slopes is
.
Solution 2
The slope of segment is . Since
is the reflection of in the
-axis, its slope is the negative of the slope of . This means
the slope of is . Similarly, the slope of segment
is , so the slope of
is . Therefore, the sum of the slopes is
.
Answer:
-
The odd numbers on the spinner are , , and
. The wedges labelled by and
each take up of the spinner and so each will be
spun with a probability of . If we let the probability of spinning
be , then we have that the probability of spinning
is . The probability of spinning either
or is , which
means or so
.
Therefore, the probability of spinning an odd number is
.
Answer:
-
Suppose and are the equations two lines. If the two
lines have the same slope, then the only way they can intersect is if they have they are the same line. To see this, suppose
and there is some such that
. Since , this equation is the same as
, which means the lines only intersect if , but this would
make the lines identical.
On the other hand, if , then the two lines will intersect in exactly one point. To see this,
suppose and . Then
, and since , we have
.
The six lines that Maggie graphs can be broken into two sets of three distinct but parallel lines. Each of the three lines with slope
intersects each of the three lines with slope exactly once by
the previous paragraph. This gives a total of intersections.
We must be sure that none of the points have been counted more than once. For this to have happened, we would need to have at least three of
the six lines intersecting in the same point. There are only two possible slopes, so among any three of the lines, at least two must have
the same slope. Therefore, if three of the lines intersect in the same point, then two distinct lines of equal slope intersect. From the
previous paragraph, this cannot happen. Therefore, the nine points are distinct, so .
Answer: 9
-
The prime factorization of is , so the prime
factorization of is
Therefore, the divisors of
are numbers of the form where
, , and are integers with
, , and
.
In order for a divisor to be a perfect square, each of , , and
must be even.
Therefore, the divisors of which are perfect squares are the numbers of the form
where is equal to
, , ,
, , or ,
is equal to , , or
, and is equal to ,
, or . This gives a total of
ways of choosing ,
, and so that is
a perfect square. This includes the divisor with corresponding to the divisor
which is a perfect square, so the answer is .
Answer: 53
-
Since , the dimensions of the larger cube must be
.
Therefore, each side of the cube has area , so the total surface of the cube is made up of
by
squares. Each of these unit squares is a face of one of the unit cubes. Since
of the surface area is red, this means
of these unit squares must be red.
For any unit cube, there are either 0, 1, 2, or 3 of its faces showing on the surface of the larger cube. The unit cube at the centre of the
larger cube has none of its faces showing, the 6 unit cubes in the centres of the outer faces have exactly one face showing, the 12 unit
cubes on the edge but not at a corner have two faces showing, one of each of two adjacent sides, and the 8 unit cubes at the corners each
have three faces showing.
This means that at most three faces of any unit cube are on the surface of the larger cube, so we cannot possibly have 18 of the unit
squares being coloured red if there are fewer than red unit cubes. There are 8 unit
cubes on the corners, so if we colour exactly 6 unit cubes red and the other 21 black, then arrange the cubes into a
cube so that the 6 red unit cubes are at the corners, there will be exactly 18 of the
unit squares on the surface coloured red. Therefore, the answer is .
Answer: 6
-
Since Gina’s rate is 7 minutes per kilometre, she runs kilometres every minute. Since
there are seconds in a minute, seconds corresponds to
minutes. As long as minutes, the distance Gina has
travelled at time is equal to
For minutes,
the distance travelled is .
The rate in minutes per kilometre that the watch will display at time is equal to
Note that this formula only works for . We will now use this to find the times at which the
watch displayed 7 minutes 30 seconds per kilometre and 7 minutes 5 seconds per kilometre.
First, 7 minutes 30 seconds per kilometre is the same as minutes per kilometre, so the
value of satisfying is the
time at which this is the rate displayed by the watch. This equation can be rearranged to
or minutes.
Next, 7 minutes 5 seconds is minutes. To find the
corresponding time, we set and rearrange to get
so .
This means that Gina was running for minutes from the time
when the app said 7 minutes 30 seconds per kilometre to the time when it said 7 minutes 5 seconds per kilometre.
While in motion, she runs at a rate of 7 minutes per kilometre. This means she runs
in this time period.
Answer: 2.5 km
-
Connect to each of , ,
, and as shown.
Each of , , , and
are radii of the circle and so are equal. As well,
since they are the side-lengths of a square, which means
, ,
, and are all congruent. This means
and since the sum of these angles must be
,
By the Pythagorean
theorem, . Since the radius of the circle is
, we have or
, so since
.
Now draw a line from through to meet
at and at
.
We know that , which means that
. Furthermore,
, , and are all radii
of the circle and hence are equal and by construction, so
and are congruent. This means
and since their sum is , we must
have .
Since is a straight line, this means
. We previously established that
is right and isosceles, which means
as well. This means
.
We now have that and are right
triangles having a common hypotenuse length and a shared side, which means they are congruent. Therefore,
. It follows that because
.
Line segments and are parallel because they are opposite
sides of a square. Therefore, and
. It follows that
.
Since , we also have that which
means . Angles and
are alternating and hence equal, and both
and are right, which means
. By similar reasoning,
is also similar to ,
, and .
Since and , we have that
, which means .
Since , we get that
Since
, this means
Since , we have that as well, and using that
, we have
Since , we have that .
This means their heights are in the same ratio as their sides. Therefore,
and since ,
, and , this means
Therefore, the area of is
The answer is .
Answer:
-
By adding , , and to
both sides of the first, second, and third equations, respectively, we get
The
left sides of these equations can now be factored. The integers on the right sides of the equations have been factored into products of
primes as well.
We are given that and are positive integers which means
is a positive integer and is an integer. This means
is a positive divisor of , so we must have that
is one of , ,
, and . We cannot have
since this would mean which is negative.
If , then
but this would mean
which is not an integer, but
must be an integer because is an integer. Therefore, we
cannot have .
If , then ,
and so . Also,
, so we have
which gives
If , then
, , and
. Therefore,
which gives
Answer: ,
-
Since , we have
which is the same as
.
Answer: 4
-
By factoring out of the numerator, we have
Answer: 6
-
Let the measure of the smallest interior angle be . Then the other three interior angles
measure , , and
.
The interior angles of a quadrilateral sum to , which means
Therefore,
, so .
Answer:
-
The numbers being summed are the multiples of from
through . Thus, if we set
to be the sum in question, we can factor out to get
It can easily be checked by hand that
. Alternatively, using the fact that for any positive integer
we have the sum can be
computed as
Therefore, .
Answer:
-
The number is an eight-digit number having exactly four digits which are 4. We will show that
this is the number we seek by showing that any other such number is larger than 10004444.
Suppose we have an eight-digit number having exactly four digits which are 4. If a digit of 4 occurs as any of the first (leftmost) four
digits, the number will be bigger than 10004444 (note that 1 is the smallest that the first digit can be since the number has eight
digits).
Otherwise, the four digits that are 4 occur as the last four digits. The smallest eight digit number ending in 4444 is 10004444.
Answer: 10004444
-
There were 200 visitors on Saturday, so there were 100 visitors the day before. Since tickets cost
on Fridays, the total money collected on Friday was .
Therefore, the amount of money collected from ticket sales on the Saturday was
.
Since there were 200 visitors on Saturday, the price of tickets on Saturday on that particular Saturday was
. Therefore, the value of is 6.
In fact, if all conditions are kept the same in this problem but the number of ticket sales on Saturday changes, the answer will still be
. You might like to try to work out why this is true.
Answer: 6
-
An integer is divisible by both and exactly when it is
divisible by . Since we seek a number having only even digits, its last digit is one of
or , so the number itself is even. Thus, we are looking
for an even multiple of . An even number is a multiple of
exactly when it is a multiple of .
Therefore, we are looking for the smallest 4-digit multiple of 90 that has only even digits.
The smallest 4-digit multiple of 90 is 1080, but the first digit of this number is 1, which is odd.
Each of the next 10 multiples of 90 has a first digit equal to 1, so the number we seek must be larger than 2000. The multiples of 90 that
are at least 2000 are and the only number in
this list that has all even digits is 2880. Therefore, 2880 is the smallest 4-digit number that is a multiple of 5, a multiple of 9, and has
only even digits.
Answer: 2880
-
The larger semicircle has diameter units. The length of a semicircular arc is
where is the diameter of the circle. This means
the length of the large semicircular arc is The diameter of
each small semicircular arc is units, so each small semicircular arc has length
There are four of these small arcs, so the perimeter of the figure is
Answer:
-
By factoring and using exponent rules, we have .
Therefore, , which is the integer 1024 followed by ten zeros. Thus,
has eleven digits that are .
Answer: 11
-
Using exponent laws, we have
Using the given condition that , we get
Answer:
-
The sum of the areas of the triangles is equal to the area of . This is because the
triangles share vertex , the base of begins
where the base of ends, the base of
begins where the base of ends,
and so on with all of , ,
, , ,
, and lie on the
-axis.
The height of is the -coordinate of
, which is . The first seven primes are
, so and
. The base of has length
. Therefore, the sum of the areas of the triangles is
Answer: 15
-
Since is a multiple of , there are
multiples of in the list. Since
is a multiple of , there are
multiples of in the list. A multiple of
is a multiple of exactly when it is a multiple of
, which means the multiples of were already crossed out when
the multiples of were crossed out. There are
multiples of in the list, so this means there
are multiples of remaining in the list once the
multiples of have been crossed out. Therefore, there are
numbers in the list once all of the multiples of and
have been crossed out.
Answer: 48
-
By completing the square, we have , which means the vertex of the parabola is
at .
If we set , we have or
, so . Taking square roots of
both sides, we have or . Therefore, the
parabola passes through and . From the information
given, this means the coordinates of are and the
coordinates of are .
The second parabola has its vertex at , so its equation is
for some real number . Using the fact that it passes
through , we get , or
.
Therefore, the equation of the second parabola is . Substituting
, we get . Therefore, the
second parabola crosses the -axis at .
Answer:
-
Since the total mass of the first three fish was kg, the average mass of the first three fish was
kg. Let be the total mass of all of the fish. Since the
average mass or the first three fish was the same as the average mass of of all of the fish,. This means
kg or kg. We can find the largest
possible mass of any individual fish by determining the smallest possible mass of any twenty of the fish, then subtracting this mass from
kg.
We first note that the answer is not kg. This is because it is possible, for example, that 19 of
the fish (including the first three) weighed kg each and the other two weighed
kg and kg. This distribution of weights satisfies all of
the conditions.
The largest fish Jeff could have caught would therefore be if 17 of the 18 fish caught after the first three weighed the minimum of
kg. This would mean the first three in addition to these 17 fish weigh
kg kg kg. The
remaining fish would weigh kg kg
kg.
-
We will assume . That is, that is the largest
of the integers. First, observe that if , then
, which means
. We are assume
, so this means we cannot have . It
follows that and are all at most
.
We will work through the possible values of for which and
can be chosen with and
.
Since , we have that .
If , then . The only perfect squares that
do not exceed are and
. It can easily be checked that is the only way
to express as a sum of three positive perfect squares. Thus, we could have
and this is the only possibility with
.
If , we have . The squares less than or
equal to are , ,
, and . The only way to write
as a sum of numbers in this list is . Thus,
is a the only possibility with .
If , we have . If
, then , and it can be checked that
cannot be expressed as a sum of positive perfect squares. Therefore,
, and since , this means
. If , then
, and since , we have
. This means we must have ,
so . The only way to write as a sum of
positive squares is , so this means
is the only possibility with .
If , then . If
, then . It can be checked that
is the only way to write as a sum of two positive
perfect squares. This means is a possibility, and it is the only possibility with
.
If , then , and it can be checked that
cannot be written as the sum of two positive perfect squares, so
. Thus, , so
. Therefore, is
the only possibility with .
Finally, if , then and
are each less than or equal to . This would mean
, so we cannot have
.
Therefore, must be one of
and the sums of the entries in these quadruples are
, , , and
, respectively. Therefore, the largest possible sum is
(and it is achievable in two different ways).
Answer: 16
-
Let be the common centre of the two circles, be the radius of
the larger circle, and be the radius of the smaller circle. Since
is tangent to the smaller circle, we have that . This
means is right-angled at . By the Pythagorean
theorem and since , we then have or
. The area of the shaded region is equal to the area of the larger circle minus the area of
the smaller circle, or . Rearranging
, we have , so the area of the shaded region
is .
Answer:
-
A quadratic function of the form with
attains its minimum at . If
, the function attains its maximum at .
For , the minimum occurs at .
The minimum value of is therefore
This is a quadratic function in the variable
. The leading coefficient is negative, so the maximum occurs at
. Therefore, the maximum of these minimum values is
.
Answer: 20
-
We will require the following fact. If and are real numbers
with , then the sum of the geometric series
is .
We will compute this sum by finding the sum and
and adding the results. For the first sum, we have
which can be rewritten as
This is a geometric series with and
. We also have that , so
the sum of the series above is
We now compute
. Similar to before, we can write the sum as
which is a geometric series with and
. Thus, its sum is
The sum
is therefore
.
Answer:
-
We need to choose 2 points out of 24, and there are
ways to do this. Two points will form a triangle
together with point unless all three points lie on a common line. Therefore, we can get the answer by
counting the number of ways to choose two points so that they and all lie on the same line and
subtract this number from 276.
We now draw every line through and some other point in the diagram. Note that many of these lines
will be the same. For example, drawing a line through and any of the other four points in the bottom
row gives the same line regardless of which of the four points is chosen. There are 13 lines in total:
Eight of these lines pass through only one of the points other than , so there cannot be a pair of
points different from on such a line that both lie on a line through
. Eliminating these lines from the diagram, we have
There are five lines remaining. Two of them contain exactly two points other than , so each of these
identifies one pair of points that, together with , do not form a triangle.
Each of the other three remaining lines contains four points other than , so each of these three lines
identifies pairs of points that, together with ,
do not form a triangle. Therefore, there are ways to choose two points from the array
that, together with , form a triangle.
Answer: 256
-
We will imagine that the track has been broken into 12 equal units. With this convention, Isabelle will begin to run once Lyla has travelled
4 units, and Isabelle will always run 5 units in the amount of time it takes for Lyla to run 4 units.
When Lyla has run a total of 4 units, Isabelle has run 0 units. At this time, Isabelle starts to run, so when Lyla has run
units, Isabelle will have run 5 units.
When Lyla has run units, Isabelle will have run
units.
When Lyla has run units, Isabelle will have run
units, and when Lyla has run units, Isabelle will
have run units. At this point, Isabelle passes Lyla for the first time.
Since Isabelle runs faster than Lyla, Isabelle will always have run farther than Lyla from this point on. The points at which Isabelle
passes Lyla will occur when Isabelle has travelled an integer number of laps, or a multiple of 12 units farther than Lyla.
This means the 5th times Isabelle passes Lyla will occur when Isabelle has gained an additional
units on Lyla.
Isabelle gains one unit on Lyla for every 4 units Lyla runs, which means that Isabelle will gain 48 units on Lyla when Lyla runs
units.
Therefore, when Isabelle passes Lyla for the 5th time, Lyla has run a total of units. There
are 12 units in a lap, so this means Lyla will have run laps.
When Isabelle passes Lyla for the 5th time, Lyla will have completed 17 laps.
Answer: 17
-
Using a log rule, we have that , so
Using the trigonometric identity
, we get
which simplifies to
and finally using the identity
for any real number , we have
and this holds for all . Therefore,
.
Answer:
-
An important observation for this problem is that every integer is either a multiple of , one more
than a multiple of , or two more than a multiple of . Suppose
is a multiple of . If
is a multiple of , then
must also be a multiple of . There are three ways this can
happen: both and are multiples of
, is one more than a multiple of
and is two more than a multiple of
, or is two more than a multiple of
and is one more than a multiple of
. If is one more than a multiple of
, then must be two more than a multiple of
. Again, there are three ways that this can happen. We summarize the possible remainders after
, , and are divided by
(either 0, 1, or 2) that will lead to being a multiple of
:
0 |
0 |
0 |
0 |
1 |
2 |
0 |
2 |
1 |
1 |
0 |
2 |
1 |
1 |
1 |
1 |
2 |
0 |
2 |
0 |
1 |
2 |
1 |
0 |
2 |
2 |
2 |
Of the numbers from to inclusive,
, , and are multiple of
(a total of three), , ,
, and are one more than a multiple of
(a total of 4), and , ,
and are two more than a multiple of (a total of 3). Thus, for
example, there are triples so that
is a multiple of and each of
, , and is a multiple of
. Computing the total for each row in the table above, we have
0 |
0 |
0 |
|
|
0 |
1 |
2 |
|
|
0 |
2 |
1 |
|
|
1 |
0 |
2 |
|
|
1 |
1 |
1 |
|
|
1 |
2 |
0 |
|
|
2 |
0 |
1 |
|
|
2 |
1 |
0 |
|
|
2 |
2 |
2 |
|
|
which means the total is
Answer:
-
We begin with a diagram. Suppose has coordinates and is
the vertex of the rectangle to the right of and on the line
. We let be the point with coordinates
and be the point with
-coordinate and lying on the line through
and .
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The area of rectangle will be twice that of ,
and we can compute the area of by subtracting the areas of
and from the area of
.
To compute these areas, we need to find the values of , , and
.
First, we find the equation of the line through and . Since
this line passes through and , it has slope
. Thus, its equation is of the form
for some . Substituting
, we have so
, which means the equation of the line is
.
To find the coordinates of , we note that the point of intersection of the diagonals of a rectangle is
equidistant from all four of its vertices.
The intersection of the diagonals will be the intersection of the lines and
. Substituting, we have
or .
Multiplying through by , we have , so
from which we get . The coordinates of
the centre of the rectangle are . The distance from this point to point
is Therefore,
is the point on the line that is
units away from . The condition on the distance gives us
or . Since
is on , we also have
which rearranges to . Substituting leads
to which can be rearranged to get
Thus, , so
. The point is to the right of the centre of the
rectangle, and since the line connecting and has negative
slope, this means should be less than . Therefore,
. Substituting into , we have
.
We now know the coordinates of , and therefore, the coordinates of
are . To find the
-coordinate of , we need only plug the known value of
in for in the equation
to get
.
The area of is
The area of is
Finally, since the height of is the horizontal distance from
to which is , we
have that the area of is
Using these three ares, we can compute the area of as
Thus, the area of rectangle is .
Answer:
-
By clearing denominators, the equation becomes which can
be expanded to get and then rearranged to
Recognizing that is a solution to the
equation above, must be a factor of the polynomial on the left, so we can factor to get
Next, is a root of
, so we can further factor from the cubic on the
left side of the above equation to get Using the quadratic formula, the roots
of the polynomial are
neither of which are real. Therefore, the only real values of that can possibly satisfy the equation
are and . It is easily check that both
and satisfy the original equation, so the answer is
.
Answer:
-
We will suppose is at the origin, which gives rise to coordinates
, ,
, and . Additionally, we will have
.
The line passing through and also passes through the origin
and has slope , and hence has equation
. The line through and
has slope
and passes through
, so if its equation is for some real
number . Substituting , we have
or . Thus, the line passing through both
and has equation
.
We can now compute the coordinates of points and . Since
is the intersection of line segments and
, the -coordinate of
satisfies or
, which can be solved to get . Since
lies on the line , this means
has coordinates .
The circle has diameter equal to the side length of the square, which is given to be . Therefore, its
radius is , which means the equation of the circle is
. Points and
are the points of intersection with the circle and the line
, which means their -coordinates can be found
by substituting in the equation of the circle for
and solving for . That is, the
-coordinates of and are
the solutions to the equation which can be expanded to get
Multiplying through by and
rearranging, we get and after dividing through by
we have We know that the
-coordinate of is a root, which means
must be a factor of the polynomial on the right, which leads to
Thus, the other solution is , so the
-coordinate of must be .
Substituting into , we get that
, so has coordinates
.
We next observe that the shaded region bund by the circle and the line segments and
is congruent to the region bound by the circle, , and
. Thus, the shaded region is equal to the sum of the areas of
and .
If we take as the base of , then its height will
be the horizontal distance from to line segment . This is
equal to the difference between the coordinates of and
, or . Thus, the area of
is
To compute the area of , we will subtract the area of
from the area of . Taking
as a common base, the heights of and
are the -coordinates of
and , respectively. These values are
and , so the area of
is
Therefore, the total area of the shaded regions is .
Answer: 510
(Note: Where possible, the solutions to parts (b) and (c) of each Relay are written as if the value of is
not initially known, and then is substituted at the end.)