Question

For an AP, if t_1=22,t_n= (-11) and s_n=66 then find n.





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Answer 1

Answer:

First term =22

nth term =-11

a+(n-1)d=-11

22+(n-1)d=-11

(n-1)d=-11-22

(n-1)d=-33

Sn=66

n/2[2a+(n-1)d]=66

n[2×22+(-33)]=132

n[44-33]=132

n×11=132

n=132/11

n=12