Q11 of 24 Page 115

The ratio of the 5th and 3rd terms of an AP is 2.5, find the ratio of the 15th and 7th terms.

Let the first term be ‘a’ and common difference be ‘d’.


We know, nth term of an AP is


an = a + (n – 1)d


Given,




⇒ 2a + 8d = 5a + 10d


⇒ 2d = –3a ……[1]


Now,






More from this chapter

All 24 →
9

If the nth term of AP – 9, 7, 5, .... is the same as the nth term of the AP – 15, 12, 9...then find the value of n.

 10

If x y z are in AP then find the value of (x+y–z) (–x+y+z).

 12

Determine k so that 2/3, k and 5k/8 are the three consecutive terms of an A.P.

 13

Which term of the A. P. 84, 80, 76.... is zero?