Question

4,12,20...........20 terms find the sum

Answer 1

Step-by-step explanation:

Here

a=4

d=8

Last term=20

a+(n-1)d=20

4+(n-1)8=20

4+8n-8=20

-4+8n=20

8n=20+4

8n=24

n=3

To find:Sn

Sn=n/2(2a+(n-1)d)

S3=3/2(2*4+2*8)

S3=3/2(8+16)

S3=3/2*24

S3=3*12

S3=36

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