Find the sum of first 15 Multiplies of 8 – InterviewSolution

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1.	Find the sum of first 15 Multiplies of 8
Answer» 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,a= 8d= 8S15= ?Sn=n/2[2a+ (n- 1)d]S15= 15/2[2(8)+ (15 - 1)8]=15/2[6 + (14) (8)]=15/2[16 + 112]= 15(128)/2= 15 × 64= 960

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