Which term of the A.P 21, 18, 15, ..... is 0?

Compute 1 + 2 + 3 + 4 + ...... + 100.

n^th term of a sequence is a + nb. Find a₄ - a₃.

The n^th term of the sequence 3, 6, 9.... is 

In a certain AP, 5 times the 5^th term is equal to 8 times the 8^th term, then its 13^th term is

If a = -5, d = 3, S_n = 110. Then the value of n is

If 103 is the first term of an AP and -22 is the common difference then the second term is

k^th term of an AP is 5k + 1. Then the sum of n terms is 

Which of the following list of numbers does not form an AP?

Find k, if the given value of x is the k^th term of the given AP.
-1, -3, -5, -7, ....;x = -151