Question

The sum of first 15multiples of 8 is

Answer 1

The multiples of 8 are
8, 16, 24,...,120

$sum = \frac{15}{2} \times (8 + 120)$

$sum = \frac{15}{2} \times 128$

$sum = 15 \times 64$
Sum = 960

Answer 2

8+16+24+32+40+48+56+64+72+80+88+96+104+112+120.=960