Question

Find the sum ofthe following APs : 1] -37, -33, -29, .......to 12 terms .​

Answer 1

Answer:

Sum of n terms of AP formula:

S

n

=

2

n

[2a+(n−1)d] ......(1)

Where

First term =a

Common difference=d

Number of terms=n

1/15,1/12,1/10,..... to 11 terms

a=1/15

d=(1/12)−(1/15)=1/60

Using (1)

S

11

=11/2[2(1/15)+(11−1)(1/60)]

=(11/2)×[(2/15)+(1/6)]

=33/20

Sum of 11 terms of this AP is 33/20.