Question

find the sum of the first 15 multiples of 8​

Answer 1

Question :

◾Sum of first fifteen multiples of 8.

Answer :

◾First 15 multiples of 8 are :–

$\sf{8,16,24,32,40,48,56,64,72,80,88,96,104,112,120}$

Now, add them.

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

━━━━━━━━━━━━━━━━━━━━━━

Hence, the answer is 960

$~~~~~~~~~~~~~~~~~~~~~{\boxed{\green{\sf{answer~is~960}}}}$

Answer 2

Answer:

a = 8

n = 15

d = 8

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

= 15/2 (2×8 + (14)8]

= 15/2 [16 +112]

= 15/2 [128]

= 15 [64]

= 960