cube root of 216 ,estimation

Question

find the cube root of the number - 216 , using estimation

 

Answer 1

To estimate the cube root of a number, group the digits of the number into 3-digit groups from right to left.  The number has only three digits, so the group is 216.

 

Then, consider the units digit (the “6”) to find a cube that ends with that digit:

      1^3 = 1

      2^3 = 8

      3^3 = d7

      4^3 = d4

      5^3 = dd5

⇒    6^3 = dd6

      7^3 = dd3

      8^3 = dd2

      9^3 = dd9

 

So, the number must end with 6

Checking 6^3, we get 216, so 6 is the number.

Answer 2

The cube root of -216 is -6

 

(-6)(-6)(-6) = 36(-6) = -216

 

Cube root of 216 is 6