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

First list :

⇒ 5 × 7, 7 × 9 and 9 × 5

⇒ 35, 63, 45

63 - 35 = 28

45 - 63 = -18

Since, common difference between consecutive terms is not equal, so it is not an A.P.

Second list :

⇒ 5 × 7, 7 × 7 and 9 × 7

⇒ 35, 49, 63

49 - 35 = 14

63 - 49 = 14

Since, common difference between consecutive terms are equal, it is an A.P.

Hence, Option 2 is the correct option.