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
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