Question

What is the thirteenth term of an arithmetic series if the third and tenth terms are 11 and 60 respectively?

• A. 74
• B. 77
• C. 81
• D. 84

Answer 1

Answer:

C. 81

Let tge first term be a, and common difference be d; 3rd term = a + 2d = 11 .......(1) 10th term= a + 9d = 60 .......(2) (2) - (1) = 7d = 49 d = 49/7 = 7 a + 3d = a + 3 × 7 = 11 a = 11 - 14 = -3 13th term=a +12d = -3 + 12 × 7 = -3 + 84 = -81