Question

What will be the sum of 5th and 7th term in A.P

Answer 1

Given : Sum of the 5th and 7th term is 52.

∴ a + 4d + a + 6d = 52

2a + 10d = 52 ...............(1)

Also given : 10th term is 46

∴ a + 9d = 46

Multiplying it by 2, we get

2a + 18d = 92 ................(2)

 Now, subtracting equation (1) from equation (2), we get.

  2a + 18d = 92

  2a + 10d = 52

-      -          -

_______________

         8d = 40 

_______________

8d = 40

d = 40/8

d = 5

 Substituting the value of d in equation (1),we get.

2a + 10d = 52

2a + 10*5 + 52

2a = 52 - 50

2a = 2

a = 2/2

a = 1

Therefore, the required AP is 1, 6, 11, 16, 21, 26, 31......

Answer.