Puzzle 85
Within the BrainBashers school, the science department has three disciplines.
In total, 280 students study chemistry, 254 students study physics, and 280 students study biology.
In total, 97 students study chemistry and physics, 138 students study physics and biology, and 152 students study chemistry and biology.
73 students study all three disciplines.
Can you determine how many students there are in the science department? The answer is not 814.
Puzzle Copyright © Kevin Stone
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Hint
How many students study chemistry and physics, but not biology?
Answer
500 students.
Reasoning
The answer is more easily seen if three intersecting circles are drawn, and the numbers inside each section are worked out.
We know that 73 students study all three disciplines, which allows us to work out the numbers.
97 students study chemistry and physics, so 97 – 73 = 24 study just chemistry and physics.
138 students study physics and biology, so 138 – 73 = 65 study just physics and biology.
152 students study chemistry and biology, so 152 – 73 = 79 study just chemistry and biology.
280 students study chemistry, so 280 – 73 – 24 – 79 = 104 study just chemistry.
254 students study physics, so 254 – 73 – 24 – 65 = 92 study just physics.
280 students study biology, 280 – 73 – 65 – 79 = 63 study just biology.
For a total of: 104 + 92 + 63 + 24 + 65 + 79 + 73 = 500 students.
Puzzle 86
How many squares, of any size, are on a board divided up into 6 squares by 6 squares?
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Hint
How many 1x1 squares are there?
Answer
91 squares.
Reasoning
Squares of size:
1 x 1 = 36
2 x 2 = 25
3 x 3 = 16
4 x 4 = 9
5 x 5 = 4
6 x 6 = 1
Total = 36 + 25 + 16 + 9 + 4 + 1 = 91.
Puzzle 87
Starting with a five-letter word, change one letter to create a new word.
This word is then changed by one letter to create another new word.
These words in turn mean:
a gaggle of geese
a device for measuring time
what you can do with a mouse
a baby chicken
a device to prevent wheels from moving
a surprise
a small house
a pile of cards
a small piece of wood
unable to move
Puzzle Copyright © Kevin Stone
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Hint
The sequence ends with STUCK.
Answers
flock = a gaggle of geese
clock = a device for measuring time
click = what you can do with a mouse
chick = a baby chicken
chock = a device to prevent wheels from moving
shock = a surprise
shack = a small house
stack = a pile of cards
stick = a small piece of wood
stuck = unable to move
Puzzle 88
A large freshwater reservoir has two types of drainage system. Small pipes and large pipes.
6 large pipes, on their own, can drain the reservoir in 12 hours.
6 small pipes, on their own, can drain the reservoir in 18 hours.
How long will 6 large pipes and 6 small pipes take to drain the reservoir?
Puzzle Copyright © Kevin Stone
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Hint
What would happen in 36 hours?
Answer
7 hours and 12 minutes.
Reasoning
We can use a time that 12 hours and 18 hours both fit in to, in 36 hours:
6 large pipes can drain 3 reservoirs.
6 small pipes can drain 2 reservoirs.
Therefore, together, 6 large and 6 small pipes can drain 5 reservoirs.
36 hours ÷ 5 = 7.2 hours for one reservoir.
7.2 hours = 7 hours and 12 minutes for one reservoir.
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