Question

Find the sum of first 20 terms of the arithmetic progression 3, 8,13..using the formula.
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Answer 1

Answer:

The first twenty terms have a sum of 1010

Step-by-step explanation:

In this problem, a=3, r=8−3=5, n=20 and s20=?.

We will use the formula sn=n2(2a+(n−1)d)

s20=202(2(3)+(20−1)5)

s20=10(6+95)

s20=10(101)

s20=1010

Hopefully this helps!