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Thursday, February 24, 2022
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Evaluating,
Answer: (C)
Solution 1
Since the average of two numbers is 7, their sum is
Since one of the numbers is 5, the other is
Solution 2
The average of two numbers is 7 and one of the numbers is 5.
Since 5 is 2 less than 7, the other number must be 2 more than 7, and so
is 9.
Answer: (E)
From the day on which she walks 500 m to the day on which she
walks 4500 m, Gauravi increases her distance by
Since Gauravi increases her distance by 500 m each day, then it takes
Starting from Monday and counting forward by 8 days (which is 1 week and
1 day) gets to Tuesday, and so Gauravi walks exactly 4500 m on a
Tuesday.
Answer: (C)
By arranging 4 rows of 4 squares of side length 2, a square of side length 8 can be formed.
Thus,
Answer: (C)
Since the list includes 15 integers, then an integer has a
probability of
The integer 5 occurs 5 times in the list and no other integer occurs 5
times, so
Answer: (E)
The given triangle can be considered to have base
The line segment joining
Point
Thus,
Answer: (D)
Evaluating,
Answer: (B)
Since
(We could have noticed initially that
Answer: (A)
Since Pearl digs 4 holes in 7 days and
Since Miguel digs 2 holes in 3 days and
In total, they dig
Answer: (D)
Manipulating the left side,
Since
This also means that
Since
Therefore,
Answer: (D)
We use
We use the notation
The five sentences give
This means that two people are older than Bev and two people are younger
than Bev, which means that Bev must be the third oldest.
Answer: (B)
Since
Since
Also,
Thus, 2 of the 4 expressions are equal to an odd integer.
Answer: (C)
Suppose that each of the small rectangles has shorter sides of
length
Then the height of the rectangle in Figure A is
Therefore, the rectangle in Figure A has height
Therefore, the ratio of the perimeter of Figure A to the perimeter of
Figure B is
Answer: (E)
Zebadiah must remove at least 3 shirts.
If he removes 3 shirts, he might remove 2 red shirts and 1 blue
shirt.
If he removes 4 shirts, he might remove 2 red shirts and 2 blue
shirts.
Therefore, if he removes fewer than 5 shirts, it is not guaranteed that
he removes either 3 of the same colour or 3 of different colours.
Suppose that he removes 5 shirts. If 3 are of the same colour, the
requirements are satisfied.
If no 3 of the 5 shirts are of the same colour, then at most 2 are of
each colour (for example, 2 red, 2 blue and 1 green). This means that he
must remove shirts of 3 colours, since if he only removed shirts of 2
colours, he would remove at most
In other words, if he removes 5 shirts, it is guaranteed that there are
either 3 of the same colour or shirts of all 3 colours.
Thus, the minimum number is 5.
Answer: (D)
If
If
Starting with
Starting with 23 and using the machine 2 times, we obtain
Starting with an odd integer and using the machine 2 times, the net
result is adding 8 to the input, because the odd input generates a first
output that is 3 larger (and so even) and a second output that is 5
larger than the first output.
This generates a net result that is
Therefore, using the machine 46 more times (that is, repeating the 2
steps a total of 23 more times), we add 8 a total of 23 more times to
obtain the output
To this point, the machine has been used 50 times.
Using the machine for the 51st time,
Answer: (B)
Since the remainder when 111 is divided by
Since
Therefore, the possible values of
Answer: (A)
Suppose that the original can has radius
Since the surface area of the original can is
When the radius of the original can is doubled, its new radius is
When the height of the original can is doubled, its new height is
Multiplying
Since
Since
Answer: (A)
Let
It takes Aria 42 minutes to walk from
(Note that 9:00 a.m. is 18 minutes after 8:42 a.m., and 9:10 a.m. is 10
minutes after 9:00 a.m..)
Since Aria walks at a constant speed, then the ratio of the distance
Since it takes 42 minutes for Bianca to walk from
Therefore, Bianca arrives at Aria’s starting point at 9:45 a.m.
(Note that 9:00 a.m. is 18 minutes after 8:42 a.m., and 9:45 a.m. is 45
minutes after 9:00 a.m..)
Answer: (D)
Since
Since
Now
Therefore,
Thus,
Since
Answer: (A)
We note that
When
As
When
When
This means that
In other words, the sum of the first
Therefore,
Answer: (E)
The total mass of the six steel bars in the bags is at least
Since the six bars are divided between three bags with the same total
mass in each bag, then the total mass in each bag is at least
There are
Each of 19 these masses is indeed possible. To see this, we note
that
which shows that 7, 8 and 9 are possible values of
Continuing to increase the larger values to 15, 14, 13, we eventually
obtain
Now, we increase the smaller values, starting from the last three
pairs:
which shows that 17, 18, 19, 20, 21, 22, 23, 24, and 25 are also
possible values of
This shows that every integer value of
In summary, there are 19 possible values of
Answer: 19
We enclose the given rectangle in a larger rectangle with
horizontal and vertical sides so that the vertices of the smaller
rectangle lie on the sides of the larger rectangle.
We will also remove the units from the problem and deal with
dimensionless quantities.
Since
Since
The height of
Now
Also,
Since
Therefore,
Finally,
Since the length of
Answer: 67
Suppose that
Suppose also that the lines with equations
Since
Since
Now
Since the point
Therefore, we want
Thus, the possible values of
The corresponding values of
Since
Thus, the possible values of
The corresponding values of
These correspond to the following values of
Using
This means that there are 7 values of
Answer: 07
Since
Since
Subtracting these two equations, we obtain
Since
Since
Since
Since
Since
Similarly,
Since
Since
Alternatively, we could note that since
Therefore,
Since
As above,
If
Subtracting
Therefore,
Since
If
Subtracting the first of these from the second, we obtain
Therefore,
Since
If
Subtracting the first of these from the second, we obtain
Therefore,
Since
The sum of these values of
The rightmost two digits of this integer are 71.
Answer: 71
Consider the grid as laid out in the problem:
We start by removing all but the integers 5,
Since the sum of the entries on each diagonal is a multiple of 5, then
Note that each of
If
If
If
If
If
We write
Similarly,
We write
This gives us
If
If
If
If
If
We can now start to consider a number of cases. Because we have seen
above that the number of possibilities for some of the entries depend on
whether or not
Case 1:
From above, there is only one choice for each of
Also,
Case 2:
Since
Also, since
Furthermore, the possibilities for the 3 empty cells are determined by
either the value of
Thus, there are 2 possibilities for each of these 3 empty cells.
Combining this information, in this case, there are thus
Case 3:
If
Next, we consider the situation when
We know here that there are two possible values for each of
Case 4:
There are 8 choices for
There are then 2 choices for
There are 2 choices for each of
Also,
This gives the grid:
We now examine the first and third columns and see that neither
One way to justify this is to note that, since
This means that
Therefore, the remaining 2 empty cells each have 2 possible entries to
make their column sums multiples of 5.
There are 8 choices for
In this case, there are thus
Finally, we look at the grids where
Case 5:
There are 8 choices for
There are then 2 choices for
There are 2 choices for each of
To see this, note that
This means that each of the empty side cells must be filled with
5.
Finally, there are 2 choices for the bottom entry (since
In this case, there are
Case 6:
There are 8 choices for
There are then 4 choices for
There 2 choices for each of
There are also 2 choices for each of the 3 remaining entries in the grid
since the two entries in each of the first column, third column and
third row do not add to a multiple of 5.
In this case, there are
Combining all of the cases, the number of possible ways to complete
the grid is
Answer: 73
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