Find the least number which must be subtracted from each of the following numbers so as to get a perfect square. Also, find the square root of the perfect square so obtained.

 (i) 402 (ii) 1989 (iii) 3250 (iv) 825 (v) 4000

(i) 402 

Here we get,

The remainder is 2 if we subtract 2 from 402 we get a perfect square.

Now finding the square root of 400 by division method

We get ,

$\sqrt{400} = 20$

(ii) 1989 

Here we get,

The remainder is 53, if we subtract 53 from 1989 we get a perfect square.

Now, finding the square root of 1936 by division method.

Therefore, $\sqrt{1936} = 44$

(iii) 3250 

Here we get ,

The remainder is 1 if we subtract 1 from 3250 we get a perfect square.

Now finding the square root of 3249 by the division method. 

Therefore, $\sqrt{3249}= 57$

(iv) 825

Here we get,

The remainder is 41, if we subtract 28 from 825 we get a perfect square.

Find the square root of 784 by the division method

Therefore, $\sqrt{784} = 28$

(v) 4000

Here we get, 

The remainder is 31, if we subtract 31 from 4000 we get a perfect square.

Find the square root of 3969 by the division method.

Therefore, $\sqrt{3969} = 63$