Question

find the sum of the first 15 multiples of 8.

Answer 1

the first multiples of 8 are


8 * 1/8×2,8*3 ... 8*15

I. e 8,16,24..... 120 which are in AP.


a = 8 , l=120 , n= 15



sum of n terms Sn = n/ 2 ( a+ l)

sum of 15 terms , S15 = 15/2(8+120)

= 15/2 × 128

= 15×64

= 960

be brainly

Answer 2

$<b><u><i>$Refer to the attachment

$<b><u><i>$We will use the formula to find the sum of first 15 multiples

$<b><u><i>$a = 8

$<b><u><i>$d = 8

$<b><u><i>$n = 15

$<b><u><i>$an = 120

$<b><u><i>$sum of 15 multiples will be 960