1.

2. How many terms of the series 2 +4+ 6amount to 42

Answer»

Let sum of n terms = 42We know sum of n terms of an APSn = n/2(2a1 + (n-1)d)

Given a1=2, d = 4-2 =2, Sn = 42

Then, 42 = n/2(2*2 + (n-1)2)42 = n (2 + n - 1)42 = n(n +1)6*7 = n(n+1)

Therefore n = 6Hence sum of 6 terms = 42


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