Check sibling questions

Ex 5.3, 2 (iii) - Chapter 5 Class 10 Arithmetic Progressions

Last updated at May 29, 2023 by

Ex 5.3, 2 - Chapter 5 Class 10 Arithmetic Progressions - Part 7

Ex 5.3, 2 - Chapter 5 Class 10 Arithmetic Progressions - Part 8
Ex 5.3, 2 - Chapter 5 Class 10 Arithmetic Progressions - Part 9

This video is only available for Teachoo black users

Subscribe Now

Learn in your speed, with individual attention - Teachoo Maths 1-on-1 Class

Book a free demo

Transcript

Ex 5.3, 2 Find the sums given below (iii) − 5 + (−8) + (−11) + ………… + (−230) − 5 + (−8) + (−11) + ………… + (−230) Here, a = –5 d = –8 – (–5) = –8 + 5 = –3 Also, Last term = 𝒍 = –230 To find sum, first we need to find n Using formula an = a + (n − 1)d Putting a = −5, d = −3, an = −230 in the formula −230 = −5 + (n − 1) × −3 −230 + 5 = (n − 1) × −3 −225 = (n − 1) × −3 (−225)/(−3) = (n − 1) 75 = n − 1 n = 75 + 1 n = 76 For sum, we use the formula S = 𝒏/𝟐 (𝒂+𝒍) Putting a = −5, n = 76, l = −230 Sn = 76/2 (−5 + (−230)) Sn = 38 (– 235) Sn = –8930

Ask a doubt
Davneet Singh's photo - Co-founder, Teachoo

Made by

Davneet Singh

Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 13 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.