Question

please answer this question ​

Answer 1

Step-by-step explanation:

120 ye 15 ka answer hai. ......

Answer 2

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Q. Find the sum of first 15 multiples of 8.

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Sum of first 15 multiples of 8.

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We know that,

The multiples of 8 are :

8, 16, 24, 32, and so on....

Therefore, as it is in an A. P. (Arithmetic progression)

Where,

a (first term) = 8

d (common difference) = 8

$\bf{S}_{n}$ = ??

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${ \underline{ \boxed{ \sf{S}_{n} \: = \frac{n}{2} [2a + (n - 1)d ]}}}$

Substitution of the given values as follows :

$\leadsto{ \sf{S}_{15} \: = \frac{15}{2} [2(8) + (15 - 1)8 ]}$

$\sf\leadsto {S}_{15} = \frac{15}{2} [16 + (14)(8) ]$

$\sf\leadsto {S}_{15} = \frac{15}{2} [16 +112 ]$

$\sf\leadsto {S}_{15} = \frac{15}{ \cancel{2}} \times \cancel{128}$

$\sf\leadsto {S}_{15} =15 \times 64$

$\sf \therefore {S}_{15} =960$

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${\underline{ \textbf{ \textsf{Sum \: of \: first \: 15 \: multiples \: of 8 \: : - 960 ans. }}}}$