Question

The first term of an ap is 12 and the last term is 90 if the sum of all the terms of the ap is 1377 then find the number of terms and common difference.

Answer 1

Common difference is 3
No.of terms is 27

Answer 2

A=12
A(n) =90
S(n) =n/2(A+A(n))=1377
1377=n/2(12+90)
1377=n*51
n=1377/51
n=27
A(n) =A+(n-1)d=90
90=12+26d
78=26d
d=78/26
d=3
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