Question

Find the sum of the following APs:

2, 7, 12, 17, ... to 19 terms.

Answer 1

The given AP is 2, 7, 12, 17,...

Here, a = 2 and d = 7 – 2 = 5

Using the formula, `S_n = n/2 [2a + (n - 1)d]`, we have

`S_19 = 19/2 [2 xx 2 + (19 - 1) xx 5]`

= `19/2 xx (4 + 90)`

= `19/2 xx 94`

= 893