Question

How many terms of the AP : 24, 21, 18, . . . must be taken so that their sum is -87

Answer 1

Answer:

-87,.....18,21,24,

a= -87 , tn = 24

d = 3

tn = a+ (n-1)d

24= -87+(n-1)3

24+87= (n-1) 3

111 = (n-1) ×3

n-1 = 111/3

n-1 = 37

n = 38

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