How many terms of the AP 26, 21 16, 11, …. are needed to give the sum 11?
To Find: Number of terms required
Let the number of terms be n.
⇒n[52 - 5n + 5] = 22⇒n(57 - 5n) = 11 × 2 = 11[57 - 5(11)]⇒n = 11
11 terms are required to give the sum 11.