Question

7th term of an arithmetic sequence is 100 and 11th term is 140.
(i) What is fifteenth term of this sequence ?

Hint:

You can find the common difference d directly using the formula d = (am - aₙ)/(m-n). Here, d = a₁₁ - a₇11-7 = (140 - 100)/(4) = (40)/(4) = 10. This is faster than setting up and solving simultaneous equations.

Answer 1