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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 has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 12 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.