Q. Find whether each of the following numbers is a perfect square or not?
(v) 69
If it is a sum of successive odd natural numbers starting with 1, then it is a perfect square.
So we try to express 69 in successive odd natural numbers. This can also be done by subtracting successive odd natural numbers from 69.
69 - 1 = 68
68 - 3 = 65
65 - 5 = 60
60 - 7 = 53
53 - 9 = 43
43 - 11 = 32
32 - 13 = 19
19 - 15 = 4
So the given number 69 is not a perfect square.