Puzzle 1
A trout's tail weighs eight pounds.
Its head weighs as much as the tail and one-half of the body combined, and the body weighs as much as the head and tail combined.
What does the whole trout weigh?
Puzzle Copyright © Kevin Stone
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Hint
A little bit of algebra might help.
Answer
64 pounds.
The head weighs 24 pounds, the body weighs 32 pounds, and the tail weighs 8 pounds.
Reasoning
The trout is made up of the head, body and tail, H, B and T.
We are told that:
T = 8
(1) H = T + B ÷ 2
(2) B = H + T
Placing T into (1) and (2) we get:
(3) H = 8 + B ÷ 2
(4) B = H + 8
Using (4) in (3) we get:
H = 8 + B ÷ 2
(5) H = 8 + (H + 8) ÷ 2
Multiplying (5) by 2 we get:
2H = 16 + H + 8
2H = 24 + H
H = 24
Therefore, by (2):
B = H + T
B = 24 + 8
B = 32
Giving:
H = 24
B = 32
T = 8
And a total of 24 + 32 + 8 = 64 pounds.
Puzzle 2
Start with a number larger than 0, square it, add 4, double, take away 3, times 4 and finally subtract the original number.
If you were now left with 20, what number did you start with?
Puzzle Copyright © Kevin Stone
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Hint
A little algebra might help.
Answer
1 /8 .
Reasoning
If we convert the question to algebra, we have:
((n^2 + 4) x 2 − 3) x 4 − n = 20
Expanding the brackets and simplifying gives:
(2n^2 + 8 − 3) x 4 − n = 20
(2n^2 + 5) x 4 − n = 20
8n^2 + 20 − n = 20
8n^2 − n = 0 (*)
8n − 1 = 0
8n = 1
n = 1 /8
In the equation marked (*) zero is also a potential solution, but as the question tells us that we "Start with a number larger than 0" we know that n can't be 0, and therefore we can safely divide by n.
Double-Checking
1 /8
squared = 1 /64
add 4 = 41 /64
double = 81 /32
take away 3 = 51 /32
times 4 = 201 /8
subtracting 1 /8 gives 20, as required.
Puzzle 3
What is the smallest positive integer, which, when multiplied by 6 …
… gives a number consisting of only 8's?
Puzzle Copyright © Kevin Stone
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Hint
Try working backwards.
Answer
148.
148 x 6 = 888.
The easiest way is to divide successive 8's by 6 until you get an integer:
8 ÷ 6 = 1.3333
88 ÷ 6 = 14.666
888 ÷ 6 = 148
Puzzle 4
You can replace the dashes with the same four-letter word, and create two new words, one that starts with ARM, and one that ends in ING.
Can you find all possible four-letter words that work?
arm----
----ing
Puzzle Copyright © Kevin Stone
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Hint
There are 4 possible answers.
Answer
Band, load, lock, and rest, all create new words:
armband and banding
armload and loading
armlock and locking
armrest and resting
Note
Some dictionaries also allow ARMRACK, but others don't. So RACK is a unofficial possible answer.
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