If the cube root of 1331 is 11 and the cube root of 1728 is 12, what is the cube root of 1442897?

(Do this one in your head - no writing or calculators allowed!)

Since 1442897 is just over 1,000,000, the cube root must be slightly over 100. If it was 110, its cube would be 1331000, still too small by a little.  Since we want the last digit cubed to end in 7, the last number must be 3, making the answer

 

113

Posted by Bryan on 2004-03-10 14:51:20