Q5 of 176 Page 8

Find the number of terms in the following A.P.'s

6, 3, 0, — 3,…..,–36

Here, a = 6 , d = 3 – 6 = –3 and l = –36


where l = a + (n – 1)d


⇒ –36 = 6 + (n – 1)(–3)


⇒ –36 = 6 –3n + 3


⇒ –36 = 9 – 3n


⇒ –36 – 9 = –3n


⇒ –45 = –3n



Hence, the number of terms in the given AP is 15


More from this chapter

All 176 →
3

Find the 10th term of the A.P.

4

Find the sum of 20th and 25th terms of A.P. 2, 5, 8, 11, ...

 5

Find the number of terms in the following A.P.'s

 6

Determine the number of terms in the A.P. 3, 7, 11, ..., 399. Also, find its 20th term from the end.