Tuesday, February 26, 2019
(in North America and South America)
Wednesday, February 27, 2019
(outside of North American and South America)
©2018 University of Waterloo
Since the largest multiple of 5 less than 14 is 10 and
Answer: (E)
Simplifying, we see that
Answer: (B)
Evaluating,
Answer: (A)
The segment of the number line between 3 and 33 has length
Since this segment is divided into six equal parts, then each part has length
The segment
The segment
Thus, the sum of the lengths of
Answer: (A)
Since 1 hour equals 60 minutes, then 20 minutes equals
Since Mike rides at 30 km/h, then in
Answer: (E)
Suppose that
Since the width of rectangle
Since
Therefore, the fraction of the rectangle that is shaded is
Answer: (C)
Since Cans is north of Ernie, then Ernie cannot be the town that is the most north.
Since Dundee is south of Cans, then Dundee cannot be the town that is the most north.
Since Arva is south of Blythe, then Arva cannot be the town that is the most north.
Since Arva is north of Cans, then Cans cannot be the town that is the most north.
The only remaining possibility is that Blythe is the town that is the most north.
The following arrangement is the unique one that satisfies the given conditions:
Blythe
Arva
Cans
Dundee
Ernie
Answer: (B)
We note that
After
Therefore, the largest integer
Answer: (C)
The average of
Answer: (E)
We find the smallest such integer greater than 30 000 and the largest such integer less than 30 000 and then determine which is closest to 30 000.
Let
Since
To make
To make
Continuing in this way, its hundreds, tens and ones digits are 578. Thus,
Let
Since
To make
Continuing in this way, its hundreds, tens and ones digits are 7, 5 and 3, respectively. Thus,
Since
Thus,
Answer: (B)
The line with equation
To find the
Further, since the two lines are perpendicular, the slopes of the two lines have a product of
Line
This means that
Therefore, the
Answer: (C)
Alberto answered 70% of 30 questions correctly in the first part.
Thus, Alberto answered
Alberto answered 40% of 50 questions correctly in the second part.
Thus, Alberto answered
Overall, Alberto answered
This represents a percentage of
Of the given choices, this is closest to 51%.
Answer: (D)
The number of minutes between 7:00 a.m. and the moment when Tanis looked at her watch was
The total number of minutes between 7:00 a.m. and 8:00 a.m. is 60.
Therefore,
The time at that moment was
Answer: (C)
Each letter A, B, C, D, E appears exactly once in each column and each row.
The entry in the first column, second row cannot be A or E or B (the entries already present in that column) and cannot be C or A (the entries already present in that row).
Therefore, the entry in the first column, second row must be D.
This means that the entry in the first column, fourth row must be C.
The entry in the fifth column, second row cannot be D or C or A or E and so must be B.
This means that the entry in the second column, second row must be E.
Using similar arguments, the entries in the first row, third and fourth columns must be D and B, respectively.
This means that the entry in the second column, first row must be C.
Using similar arguments, the entries in the fifth row, second column must be A.
Also, the entry in the third row, second column must be D.
This means that the letter that goes in the square marked with
We can complete the grid as follows:
Answer: (B)
Since 4 balls are chosen from 6 red balls and 3 green balls, then the 4 balls could include:
4 red balls, or
3 red balls and 1 green ball, or
2 red balls and 2 green balls, or
1 red ball and 3 green balls.
There is only 1 different-looking way to arrange 4 red balls.
There are 4 different-looking ways to arrange 3 red balls and 1 green ball: the green ball can be in the 1st, 2nd, 3rd, or 4th position.
There are 6 different-looking ways to arrange 2 red balls and 2 green balls: the red balls can be in the 1st/2nd, 1st/3rd, 1st/4th, 2nd/3rd, 2nd/4th, or 3rd/4th positions.
There are 4 different-looking ways to arrange 1 red ball and 3 green balls: the red ball can be in the 1st, 2nd, 3rd, or 4th position.
In total, there are
Answer: (A)
Since
Since the area of the given figure is 252, then
Since
The perimeter of the figure consists of 16 segments of length
Therefore, the perimeter is
Answer: (A)
Join
Since
Since pentagon
Thus,
Each interior angle in a regular pentagon measures
Since
Since
Thus,
By symmetry,
Finally,
Answer: (B)
Let
The leftmost digit of
Since
Therefore,
Since the ones digit of
The sum of the digits of
Since each of
Thus,
That is,
There are 10 ways for 2 of these to be 1s.
These correspond to the pairs
There is 1 way for all 5 of
Thus, there are
Answer: (B)
We use the functional equation
Setting
Setting
Setting
Setting
Setting
Answer: (D)
Suppose that a circle with centre
Join
Join
Since the radius of the circle is 2, then
By symmetry,
Since these three angles add to
Since
Therefore,
Since
Since
Therefore, the area of
Since
This means that the area of
Answer: (A)
Solution 1
We start with the ones digits.
Since
Looking at the tens column, since
Looking at the hundreds column, since
Looking at the thousands column, since
Looking at the ten thousands column, since
Looking at the hundred thousands column,
This gives the following completed multiplication:
Finally,
Solution 2
Let
This means that
Also,
From the given multiplication,
Thus,
Since
Answer: (A)
Let
Since
Since
Let
Since
Also,
Since
Since
By the Pythagorean Theorem,
Answer: (B)
We consider first the integers that can be expressed as the sum of exactly 4 consecutive positive integers.
The smallest such integer is
We note that when we move from
Therefore, the positive integers that can be expressed as the sum of exactly 4 consecutive positive integers are those integers in the arithemetic sequence with first term 10 and common difference 4.
Since
Next, we consider the positive integers
The smallest such integer is
Using an argument similar to that from above, these integers form an arithemetic sequence with first term 15 and common difference
Since
When we exclude the integers already listed above (30, 50, 70, 90), we obtain
Next, we consider the positive integers
These integers form an arithmetic sequence with first term 21 and common difference 6.
Since
When we exclude the integers already listed above (45, 75), we obtain
Since
Therefore, if an integer
We make a table to enumerate the
New |
|||
---|---|---|---|
7 | 28 | 28, 35, 42, 49, 56, 63, 70, 77, 84, 91, 98 | 28, 49, 56, 77, 84, 91 |
8 | 36 | 36, 44, 52, 60, 68, 76, 84, 92, 100 | 36, 44, 52, 68, 76, 92 |
9 | 45 | 45, 54, 63, 72, 81, 90, 99 | 72 |
10 | 55 | 55, 65, 75, 85, 95 | None |
11 | 66 | 66, 77, 88, 99 | 88 |
12 | 78 | 78, 90 | None |
13 | 91 | 91 | None |
In total, there are
What do you notice about the
Answer: (B)
A quadratic equation has two distinct real solutions exactly when its discriminant is positive.
For the quadratic equation
We also want both of the solutions of the original quadratic equation to be negative.
If
In this case, if
This means that, if
Thus, it must be the case that
So we consider
This quadratic is of the form
We know that this equation has two distinct real solutions.
Suppose that the quadratic equation
This means that the factors of
In other words,
Now,
Since
If
If
If
Knowing that the equation
Here,
Finally, this means that the equation
This means that
Answer: (E)
In this solution, we will use two geometric results:
The Triangle Inequality
This result says that, in
This result comes from the fact that the shortest distance between two points is the length of the straight line segment joining those two points.
For example, the shortest distance between the points
The Angle Bisector Theorem
In the given triangle, we are told that
The Angle Bisector Theorem can be proven using the sine law:
In
, we have .
In, we have .
Dividing the first equation by the second, we obtainSince , then .
Since, then .
Combining these three equalities, we obtain, as required.
We now begin our solution to the problem.
By the Angle Bisector Theorem,
Therefore, we can set
By the Triangle Inequality,
This is equivalent to the inequality
Since
Using the Triangle Inequality a second time, we know that
This is equivalent to
Since
(Since we already know that
The perimeter,
Since
Since
Since
Since
Every possible value of
We know that the smallest possible integer value of
The number of integers in this range is
Therefore, we obtain the following equivalent equations:
For an example of such a triangle, suppose that
Here,
The number of integers between 17 and 23, inclusive, is 7, which equals
Answer: (A)