# Find the Sum of First 15 Multiples of 8. - Mathematics

Find the sum of first 15 multiples of 8.

#### Solution

The multiples of 8 are

8, 16, 24, 32…

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

Therefore, a = 8

d = 8

S15 =?

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

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

=15/2[16+14(8)]

=15/2(16+112)

= (15(128))/2 = 15xx64

= 960

Therefore, the sum of the first 15 multiples of 8 is 960

Concept: Sum of First n Terms of an AP
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#### APPEARS IN

NCERT Class 10 Maths
Chapter 5 Arithmetic Progressions
Exercise 5.3 | Q 13 | Page 113
RD Sharma Class 10 Maths
Chapter 5 Arithmetic Progression
Exercise 5.6 | Q 12.1 | Page 51