Find the sum of first 22 terms of an A.P. in which d = 22 and a₂₂ = 149.

The first term of an A.P. is 2 and the last term is 50. The sum of all these terms is 442. Find the common difference.

If 12^th term of an A.P. is 13 and the sum of the first four terms is 24, what is the sum of first 10 terms?

Find the sum of all natural numbers between a and 100, which are divisible by 3.

Find the sum of first n odd natural numbers.