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Puzzle ZHAI 



??

Which is larger:

the tenth root of 10, or the cube root of 2?

Puzzle Copyright © Kevin Stone

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Answer
Cube root of 2.

Reasoning
We could use a calculator to see that the tenth root of 10 = 1.2589 and the cube root of 2 = 1.2599.

But, if you've not got your calculator handy...

We have:

   101/10 vs 21/3

Raise each to the power of 30 (since 10 x 3 = 30) to give:

   (101/10)30 vs (21/3)30

   101/10 x 30 vs 21/3 x 30

   103 vs 210

   1000 vs 1024

Therefore, the cube root of 2 is larger.

 

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