In an A.P., given a_n = 4, d = 2, S_n = -14, find n and a.

In an A.P., given a = 3, n = 8, S = 192, find d.

How many terms of the AP : 9, 17, 25,……. must be taken to give a sum of 636?

The first term of an AP is 5, the last term is 45 and the sum is 400. Find the number of terms and the common difference.