Puzzle 57
What is the smallest positive integer which, when multiplied by 7, gives an answer consisting of only 4's?
Puzzle Copyright © Kevin Stone
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Hint
It will take a while to check 1 x 7, 2 x 7, 3 x 7. What do we know about the answer?
Answer
63,492 x 7 = 444,444
Reasoning
We can work backwards, as we know that the number multiplied by 7 has only 4's. We can try the following:
4 ÷ 7 ≈ 0.57 x
44 ÷ 7 ≈ 6.29 x
444 ÷ 7 ≈ 63.43 x
4,444 ÷ 7 ≈ 634.86 x
44,444 ÷ 7 ≈ 6,349.14 x
444,444 ÷ 7 = 63,492
Puzzle 58
What word can prefix (go before) these letters to make a valid word in each case:
..ir
..ad
..lm
..ed
..lp
Puzzle Copyright © Kevin Stone
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Hint
The missing word is two letters long.
Answer
He.
To give:
..ir = heir
..ad = head
..lm = helm
..ed = heed
..lp = help
Puzzle 59
Painter Pete, our local DIY expert, is renovating the local hospital.
He has to number each of the rooms in the hospital with plastic numbers.
However, he has run out of the number 9.
Unfortunately, he has no spare 6's available, which certainly would have been useful.
How many 9's must Pete buy in order to number all 1,000 rooms?
Puzzle Copyright © Kevin Stone
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Hint
Don't forget the extra 9's in 90, 91, etc.
Answer
300.
Reasoning
Start with: 9, 19, 29, 39, 49, 59, 69, 79, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99 – which is 20 9's.
We then repeat this for 100, 200, 300, up to 900 – which is 200 9's.
But from 900 to 999 we have an extra 100 9's as each starts with a 9.
So the total is 300.
Puzzle 60
Can you find a three-letter word that completes these words?
b---
d---
m---et
p---ing
sh---
Puzzle Copyright © Kevin Stone
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Hint
One possible answer begins with the letter A.
Answer
ark: bark, dark, market, parking, shark.
or:
ill: bill, dill, millet, pilling, shill.
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