Puzzle 17
I was quite bored yesterday, so I visited my local animal sanctuary.
To pass the time, I counted 612 legs.
This came from an equal number of beetles, spiders, and mice.
Can you work out the total number of animals I counted?
Puzzle Copyright © Kevin Stone
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Hint
A beetle has six legs, a spider has eight legs, and a mouse has four legs.
Answer
102 animals, 34 of each.
Reasoning
As there are the same number of each animal, for every beetle, spider, and mouse counted, there are a total of 18 legs.
612 ÷ 18 = 34 of each animal.
Which gives a total of 34 x 3 = 102 animals.
Puzzle 18
Place all of the digits from 1 to 9 into the circles so that the sum of the numbers in each straight line is the same.
Puzzle Copyright © Cihan Altay
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Hint
Each line adds to 14.
Answer
Puzzle 19
What is missing from this sequence:
Greenland · New Guinea · Borneo · Madagascar · ? · Sumatra · Honshu
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Hint
These are all islands.
Answer
Baffin Island.
From the largest islands in the world, in descending order.
Australia is considered the smallest continent, and Greenland the largest island.
Puzzle 20
I recently went to the shop and purchased 4 items.
Three of the items cost:
$1.50
$3.00
$4.00
There was quite a long queue, and as I was quite bored, I was playing with my pocket calculator while I waited.
Very curiously, the 4 prices added to the same number as I got when I multiplied the 4 prices together.
What was the price of the 4th item?
Puzzle Copyright © Kevin Stone
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Hint
What do the 3 numbers add to, and multiply to, so far?
Answer
$0.50.
Reasoning
The three prices add to 1.50 + 3.00 + 4.00 = 8.50.
The three prices multiply to 1.50 x 3.00 x 4.00 = 18.00.
You might be able to see that adding another 0.50 will take the total to 9.00, and multiplying by another 0.50 will take the product to 9.00.
The answer can also be found using algebra. If we call the missing price P, we have:
1.50 + 3.00 + 4.00 + P = 1.50 x 3.00 x 4.00 x P
8.50 + P = 18.00 x P
8.50 = 18.00 x P − P
8.50 = 17.00 x P
8.50 ÷ 17.00 = P
P = 0.50.
