Question

2+7+12......…in this a.p sum of the first 20 terms
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Answer 1

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We know, Sum of n terms is Sn=2n[2a+(n−1)d]

a= First term =2

d= Common difference =7−2=5

n= number of terms =20

S20=220[2(2)+(20−1)5]

S20=10[4+95]

S20=10(99)

S20=990