Question

The first term of an arithmetic sequence is 1 and the sum of the first four terms is 100.

Find the first four terms.

Answer 1

First term f = 1

If first four terms are

f, f + d, f + 2d, f + 3d

f + f + d + f + 2d + f + 3d = 100

4f + 6d = 100

= 2f + 3d = 50

2 + 3d = 50

= 3d = 50 – 2 = 48

d = 16

The arithmetic sequence is 1, 17, 33, 49, ………….