Solution:
The multiples of 8 are 8, 16, 24, 32…
The series is in the form of AP, with the first term as 8 and the common difference as 8.
Therefore, a = 8
d = 8
S15 = ?
By the formula of the sum of n terms, we know,
Sn = n /2 [2a + (n – 1) d ]
S15 = 15/2 [2(8) + (15 – 1)8]
= 15/2[16 + (14)(8)]
= 15/2[16 + 112]
= 15(128)/2
= 15 × 64
= 960