Advertisement Remove all ads

The 4th Term of an A.P. is 22 and 15th Term is 66. Find the First Terns and the Common Difference. Hence Find the Sum of the Series to 8 Terms. - Mathematics

The 4th term of an A.P. is 22 and the 15th term is 66. Find the first terns and the common
difference. Hence find the sum of the series to 8 terms.

Advertisement Remove all ads

Solution

Let a be the first term and d be the common difference of given A.P.

Now,

4th term = 22

⇒ a + 3d = 22 ...(i)

15th  term = 66

⇒ a + 14d = 66

 Subtracting (i) from (ii), we have

11d = 44

⇒ d = 4

Substituting the value of d in (1) we get

a = 22 - 3 x 4 = 22 - 12 =10

⇒ First term = 10

Now

Sum of 8 terms = `8/2[2xx10+7xx4]` = 4[20+28] = 4x48=192

  Is there an error in this question or solution?
Advertisement Remove all ads

APPEARS IN

Advertisement Remove all ads
Advertisement Remove all ads
Share
Notifications

View all notifications


      Forgot password?
View in app×