Question

i) Find the sum of first 15 multiples of 8
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Answer 1

Answer:

Sum of the first 15 positive integers is 15*(15+1)/2 = 120

Sum of the first 15 multiples of 8 is 8*120 = 960

Sum of the first 15 positive integers is 15*(15+1)/2 = 120

Sum of the first 15 multiples of 8 is 8*120 = 960

Step-by-step explanation:

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