Puzzle 729
What is the 10th prime number?
2, 3, 5, 7, …
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Hint
2, 3, 5, 7, 11, 13, 17, 19, 23, …
Answer
29.
The first ten prime numbers are: 2, 3, 5, 7, 11, 13, 17, 19, 23, 29.
Puzzle 730
My shirt has 5 buttons, my cardigan has 2 buttons, and my suit jacket has no buttons.
How many buttons do my trousers have?
Puzzle Copyright © Kevin Stone
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Hint
It depends on the length of the word.
Answer
2 buttons.
The number of buttons is 10, minus the length of the word.
Puzzle 731
Sam takes 20 days to build a wall.
Taylor and Kelly each take 10 days to build a wall.
How long will it take the three of them to build a wall if they work together?
Puzzle Copyright © Kevin Stone
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Hint
How much of a wall does Sam build in one day?
Answer
4 days.
Reasoning
In one day, Sam can build 1/20 of a wall, Taylor and Kelly can each build 1/10.
So, in one day, in total, they can build 1/20 + 1/10 + 1/10 = 1/4.
Therefore, the wall will take 4 days to build.
Puzzle 732
What is the smallest 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
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