The sum of n terms of an A.P. is 3n². The second term of this A.P. is :

1. 8

2. 3

3. 9

4. 12

If 5, 7 and 9 are in A.P. then which of the following is in A.P.?

1. 5 × 7, 7 × 9 and 9 × 5

2. 5 × 7, 7 × 7 and 9 × 7

3. 2 × 5, 2 × 7 and 5 × 9

4. 5 - 7, 7 - 9 and 9 - 5

The sum of three consecutive terms of an A.P. is 21 and the sum of their squares is 165. Find these terms.

The angles of a quadrilateral are in A.P. with common difference 20°. Find its angles.