Q. Find whether each of the following numbers is a perfect square or not?
(iv) 49
If it is a sum of successive odd natural numbers starting with 1, then it is a perfect square.
So we try to express 49 in successive odd natural numbers. This can also be done by subtracting successive odd natural numbers from 49.
49 - 1 = 48
48 - 3 = 45
45 - 5 = 40
40 - 7 = 33
33 - 9 = 24
24 - 11 = 13
13 - 13 = 0.
Hence 49 is a perfect square number.