Question

find the sum of the first 15 multiplies of 8​

Answer 1

Answer:

The multiples of 8 are 8,16,24,32…

These are in an A.P., having first term as 8 and common difference as 8.

Therefore, a=8,d=8, S

15

=?

S

n

=

2

n

[2a+(n−1)d]

S

15

=

2

15

[2(8)+(15−1)8]

=

2

15

[16+(14)(8)]

=

2

15×128

=960