Question

In an A.p. the first term is 22, nth term is -11 and the sum to first n terms is 66. Find n and d, the common difference.

Answer 1

Answer:

12

Step-by-step explanation:

a = 22

tn = -11

sn = 66

tn = a + (n-1)d

-11= 22 + (n-1)d

(n-1)d = -33

sn = n/2 {2a + (n-1)d}

66 = n/2 (44-33)

66 = 11n/2

n = 66 × 2/11

= 6 × 2 = 12