Question

Find the 120th term of the following sequence
7, 14, 21, ...
a120 =

Answer 1

840

Explanation:

There is a common difference d between consecutive terms, that is

d = 14 - 7 = 21 - 14 = 7

This indicates the sequence is arithmetic with n th term

`a_(n)` = a₁ + (n - 1)d

where a₁ is the first term and d the common difference

Here a₁ = 7 and d = 7 , thus

`a_(120)` = 7 + (119 × 7 ) = 7 + 833 = 840