Question

7^th term of an A.P. is 40, then the sum of first 13 terms is

• A. 53
• B. 520
• C. 1040
• D. 2080

Answer 1

Answer: (B)

520

Answer 2

$S_{13} = \frac{13}{2}\{ 2a + 12d\} = 13\{ a + 6d\} = 13 \times T_{7} = 13 \times 40 = 520$