Question

Examine if $398$ is a perfect cube. If not, then find the smallest number that must be subtracted from $398$ to obtain a perfect cube.

Answer 1

We know that

$7^3=343$

$8^3=512$

So, clearly $398$ is not perfect cube.

$398-343=55$

So, $55$ must be subtracted from $398$ to make it perfect cube.

Hence, this is the answer.