Question

find the sum of the first 15 multiplies of 8find the sum of the first 15 multiples of 8 ​

Answer 1

The sum of 15 multiples of eight is 440

and

8 multiples of 15 is 660

Answer 2

Answer:

a = 8

n = 15

d = 8

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

= 15/2 (2×8 + (14)8]

= 15/2 [16 +112]

= 15/2 [128]

= 15 [64]

= 960