SECTION:C(3X81. Find the sum of the first 15 multiples of 8.

1.	SECTION:C(3X81. Find the sum of the first 15 multiples of 8.
Answer» $\huge\bf\pink{\mid{\overline{\underline{Answer :- }}}\mid}$ We know that the, Multiple of 8 are :- 8 , 16 , 24 , 32 , 40, 48 , 56, 64 , 72 , 80 , 88 , 96,----------------,n According to the QUESTION, The sum of the first 15 multiples of 8. Using A.P. We know that the sum of first n TERMS are :- Sn = $\dfrac{n}{2} (2a + (n - 1)d)$ Where, n = no. of terms = 15 a = term = 8. a2 = 16 d = COMMON difference = a2 - a = 16 - 8 = 8 ➝ Sn = $\dfrac{15}{2} (2 \times 8 + (15 - 1)8)$ ➝ $\dfrac{15}{2} (16 + (14)8)$ ➝ $\dfrac{15}{2} (16 + 112 )$ ➝ $\dfrac{15}{2} (128 )$ ➝ 7.5 × 128 ➝ 960

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