Find the square root of 324.
So, we have two choices, 12 and 18, and digital sum of the square is 9 or 0, and so is the case with the squares of 12 and 18. So, the number in the tenths digit of the square will have to come to the rescue.
If we choose 12, the number in the tenths digit of the square root will be
1x2 + 1x 2 = 4 which is not so in the square.
If we choose 18, then the number in the tenths digit of the root will be found from: ……. 1x8 + 1x 8 =16 8x8 =64. so that the number in the tenths digit becomes 16 + 6 ending in 2 in that place Hence, 18 is the required square root.