Answers

2015-06-05T22:33:09+05:30
648 = 2 × 2 × 2 × 3 × 3 × 3 × 3
In the prime factors, only 2 and 3 are present. 2 form a triplet (there are three 2s), while there are four 3s.To be a perfect cube, all prime factors should be in multiples of 3. Therefore, to make 648 a perfect cube, it has to be multiplied by 3 × 3 = 9 (so that there will be six 3s in total).

P.S. You can also multiply by  \frac{1}{3} , which is smaller or by  \frac{1}{648} , which is even smaller, but the officially accepted answers are integers, unless they specify otherwise.
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2015-06-06T10:00:11+05:30
648=2*2*2*3*3*3*3
To make it a perfect cube, either it has to be multiplied by 9 or 1/3
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