Find the sum of the first 20 terms in an arithmetic progression whose first term…

Find the sum of the first 20 terms in an arithmetic progression whose first term is 7 and last term is 117.

Correct Answer: Option B

Explanation

Given the first and last term of an A.P, the sum of the terms is given by

(S_{n} = frac{n}{2} [a + l])

where a = first term; l = last term and n = number of terms.

(therefore S_{20} = frac{20}{2} [7 + 117])

= (10 (124))

= 1240