Question

Find the sum of first 15multiplied of 8

Answer 1

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.

Answer 2

$Here$  $is$   $your$   $Answer$

The multiples of 8 are

8, 16, 24, 32…

These are in an A.P., having first term as 8 and common difference as 8.

Therefore, a = 8

d = 8

S15 = ?

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

S15 = 15/2 [2(8) + (15 - 1)8]

= 15/2[6 + (14) (8)]

= 15/2[16 + 112]

= 15(128)/2

= 15 × 64

= 960