Question

Find the sum of the first 15 multiples of 8.​

Answer 1

Sum of these numbers forms an arithmetic series 8 + 16 + 24 + … + 120.

Here, first term = a = 8

Common difference = d = 8

Sum of n terms of this arithmetic series is given by:

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

Therefore sum of 15 terms of this arithmetic series is given by:

∴ S15 = 15/2[2(8) + (15 - 1)(8)]

= (15/2) [16 + 112]

=(15/2) × 128

= 15 × 64

= 960

Answer 2

Answer:

s=15/2 (2*8 + 14*8)

=15/2(16+112)

=1920/2

= 960

Mark this as brainliest.