Find the sum of the first 15 multiples of 8( arithmetic progression)

1.	Find the sum of the first 15 multiples of 8( arithmetic progression)
Answer» The answer is 960 The first 8 multiples of 8 are8, 16, 24, 32, 40, 48, 56,64These are in an A.P., having first term as 8 and common difference as 8.Therefore,\xa0a\xa0= 8d\xa0= 8S15\xa0= ?Sn\xa0=\xa0n/2\xa0[2a\xa0+ (n\xa0- 1)d]S15\xa0= 15/2\xa0[2(8)\xa0+ (15 - 1)8]=\xa015/2[6 + (14) (8)]=\xa015/2[16 + 112]= 15(128)/2= 15 × 64= 960\xa0 The answer is 960

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