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} = *n*/2 [2*a* + (*n* - 1)*d*]

*S*_{15} = 15/2 [2(8) + (15 - 1)8]

= 15/2[6 + (14) (8)]

= 15/2[16 + 112]

= 15(128)/2

= 15 × 64

= 960