Question

The sum of first four terms of an

a.P is 56. The sum of last four terms of same

a.P is 112. The first term of the

a.P is 11. Find the number of terms in that

a.P.

Answer 1

First term is 11

S4=56

=>2 (2×11+3d)=56

=>d=2

Let total no of terms n

Sn=n÷2 (2a+(n-1)d)

112=n (n+10)

Therefore

N=7 approximately

Answer 2

Answer:

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