Question

The 7th term and 17th term of an A.P. are 24 & 54 respectively find the 12th term of this A.P.

Answer 1

Answer:

39

Step-by-step explanation:

    Let the first term be 'a' and common difference be 'd'.

7th term = 24

⇒ a + 6d = 24         ...(1)

17th term = 54

⇒ a + 16d = 54        ...(2)

Adding (1) and (2), we get

⇒ (a + 6d) + (a + 16d) = 24 + 54

⇒ 2a + 22d = 78

⇒ 2(a + 11d) = 78

⇒ a + 11d = 39         ...(3)

Therefore, 12th term

⇒ a + 11d

⇒ 39             [from (3)]

Solved using:

      nth term = a + (n - 1)d