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Find the sum of the first 15 multiples of 8.
Find the sum of the first 15 multiples of 8.
Updated On: Jan 13, 2026
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Solution and Explanation
The multiples of 8 are \(8, 16, 24, 32….\) These form an arithmetic progression (A.P.) with a first term of 8 and a common difference of 8. Thus, \(a = 8\) and \(d = 8\). We need to find \(S_{15}\). The formula for the sum of the first \(n\) terms of an A.P. is \(S_n = \frac n2 [2a +(n-1)d]\).
Substituting the values for \(S_{15}\): \(S_{15}= \frac {15}{2} [2(8) +(15-1)8]\)
Simplifying the expression: \(S_{15}= \frac{15}{2} [16 +14(8)]\)
\(S_{15}= \frac {15}{2} [16 +112]\)
\(S_{15}= \frac {15 \times (128)}{2}\)
\(S_{15}= 15 \times 64\)
\(S_{15}= 960\)
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