Find the least number which must be subtracted from each of the following 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

In order to find the least number to be subtracted from the given no., we must find a smaller perfect square number, closest to the given number.
i)402
The closest smaller perfect square number is 400
Difference=402−400=2
Hence, 2 must be subtracted from 402 in order to make it a perfect square.
∴√400=20
ii)1989
The closest smaller perfect square number is 1936.
Difference=1989−1936=53
Hence, 53 must be subtracted from 1989 in order to make it a perfect square.
∴√1936=44
iii)3250
The closest smaller perfect square number is 3249.
Difference=3250−3249=1
Hence, 1 must be subtracted from 3250 in order to make it a perfect square.
∴√3249=57
iv)825
The closest smaller perfect square number is 784.
Difference=825−784=41
Hence, 41 must be subtracted from 825 in order to make it a perfect square.
∴√784=28
v)4000
The closest smaller perfect square number is 3969.
Difference=4000−3969=31
Hence, 31 must be subtracted from 4000 in order to make it a perfect square.
∴√3969=63