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Find the sum of first 15 multiples of 8? [with Video] - Teachoo

Ex 5.3, 13 - Chapter 5 Class 10 Arithmetic Progressions - Part 2


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Ex 5.3, 13 Find the sum of first 15 multiples of 8. Multiples of 8 are 8, 16, 24,… Since difference is same, it is an AP We need to find sum of first 15 multiples We use formula Sn = 𝑛/2 (2π‘Ž+(π‘›βˆ’1)𝑑) Here, n = 15, a = 8 & d = 16 – 8 = 8 Putting values in formula Sn = 𝒏/𝟐 (πŸπ’‚+(π’βˆ’πŸ)𝒅) = 15/2(2 Γ— 8+(15βˆ’1) Γ— 8) = 15/2 (16+14 Γ— 8) = 15/2 (16+112) = 15/2 Γ— 128 = 960 Therefore, the sum of first 15 multiples of 8 is 960

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Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 12 years. He provides courses for Maths and Science at Teachoo.