The n^th term of an A.P. is 6n + 4. The sum of its first two terms is :

1. 16

2. 20

3. 26

4. none of these

How many terms of the A.P. :

24, 21, 18, ……….. must be taken so that their sum is 78 ?

Find the sum of all odd natural numbers less than 50.

Find the sum of first 12 natural numbers each of which is a multiple of 7.