Second term in an AP is 8 and the 8th term is 2 more than thrice the second term Find the sum up to ...........

Quantitative Aptitude ( CCS) Arithmetic progression

Second term in an AP is 8 and the 8th term is 2 more than thrice the second term. Find the sum up to 8 terms of this AP.

124

108

110

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Explanation:

Given, Second term of an AP is 8 => a+d =8, 8th term is 2 more than thrice the second term
=> a+7d = 2 +3(a+d) = 2+3*8 =26 .
a+d =8 -------------- 1
a+7d = 26 -------------- 2
Solving for d in the two equations, we get d = 3 and a =5.
Sum of n terms in an AP = n/2 * [2a +(n-1)d].
=> Sum upto 8 terms in this AP = 8/2 * [2*5 + (8-1)3] => 4*[10+21] = 4*31 = 124.