Question

How many terms of the AP 63, 60, 57, 54, ….. must be taken so that their sum is 693? Explain the double answer.

Answer 1

The given AP is 63, 60, 57, 54,………..

Here, a = 63 and d = 60 - 63 = -3

So, the sum of 21 terms as well as that of 22 terms is 693. This is because the 22^nd term of the AP is 0.

Hence, the required number of terms is 21 or 22.