Question

find the sum of the first 15 multiples of 8

Answer 1

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First Term (a) = 8
Common Difference (d) = 8
Number of terms (n) = 15

So, Sn = n/2 [2a + (n-1)d ]
Sn = 15/2 [2(8) + 14(8)]
Sn = 15/2 [16 + 112]
Sn = 15/2 [128].
Sn = 15 [64]
Sn = 960.....
So,Sum of first 15 multiples of 8 is 960✔✔
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Answer 2

Hello,

Question;-

Find the sum of the first 15 multiplies of 8

Method of Solution;-


Let to be a is first term and 'd'" is common Difference and l is last term of Given Arithmetic Sequence or Progression;-

Arithmetic Sequence or Progression which are given below;-

Arithmetic Sequence or Progression;-

8,16,24,32....

Here,

First term= 8

CommOn Difference=8

Number of terms=15

We know that Formula of Summation of Arithmetic Sequence or Progression.

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

S15=15/2(2x8+(15-1)8

  =15/2(16+(14)8)

  =15/2(16+112)

  =15/2 x 128

  =15 x 64

 =960


Hence ,960 are sum of the first 15 multiples of 8.