Find the greatest five-digit number, which is a perfect square.

Given :

The given statement is 'the greatest five-digit number which is a perfect square'.

To do :

We have to find such a number.

Solution :

The greatest 5 digit number is 99999.

To find the largest 5 digit number which is a perfect square, first, we have to find out the smallest number which should be subtracted from this number to obtain a perfect square.

For this, we apply the method of finding the square root of 99999 by division method.

The remainder is 143.

Therefore, if we subtract 143 from 99999 then the new number will be a perfect square.

The required number is $99999 - 143 = 99856$.