# Ex 9.1, 9 - Chapter 9 Class 7 Rational Numbers

Last updated at June 22, 2018 by Teachoo

Last updated at June 22, 2018 by Teachoo

Transcript

Ex 9.1, 9 Which is greater in each of the following: (i) 2/3, 5/2 2/3, 5/2 Here, denominator is different So, we make denominator same Common denominator = L.C.M of 2 & 3 = 2 ร 3 = 6 So, 2/3 = 5/2 = Therefore, 4/6 < 15/6 i.e. 2/3 < 5/2 So, ๐/๐ is greater Ex 9.1, 9 Which is greater in each of the following: (ii) (โ5)/6, (โ4)/3 (โ5)/6, (โ4)/3 Since both numbers are negative, We ignore the signs 5/6 & 4/3 We compare these two numbers Since denominator is different, we make it same. Common denominator = L.C.M of 3 & 6 = 2 ร 3 = 6 So, 5/6 = 4/3 = Therefore, 5/6 < 8/6 i.e. 5/6 < 4/3 Multiplying โ1 both sides 5/6 ร โ1 > 4/3 ร โ1 (โ5)/6 > (โ4)/3 So, (โ๐)/๐ is greater. Ex 9.1, 9 Which is greater in each of the following: (iii) (โ3)/4, 2/(โ3) (โ3)/4, 2/(โ3) i.e. (โ3)/4, (โ2)/3 Since both numbers are negative, We ignore the signs 3/4 & 2/3 We compare these two numbers Common denominator = L.C.M of 4 & 3 = 2 ร 2 ร 3 = 12 So, 3/4 = 2/3 = Therefore, 9/12 > 8/12 i.e. 3/4 > 2/3 Multiplying โ1 both sides 3/4 ร โ1 < 2/3 ร โ1 (โ3)/4 < (โ2)/3 So, (โ๐)/๐ is greater. (โ1)/4, 1/4 Since positive number is always greater than negative number. 1/4 & (โ1)/4 So, ๐/๐ is greater Ex 9.1, 9 Which is greater in each of the following: (v) โ3 2/7, โ3 4/5 โ3 2/7, โ3 4/5 โ3 ๐/๐ = โ (3+2/7) = โ ((3 ร 7 + 2)/7) = โ ((21 + 2)/7) = (โ23)/7 โ3 ๐/๐ = โ (3+4/5) = โ ((3 ร 5 + 4)/7) = โ ((15 +4)/5) = (โ19)/5 So, we have to compare (โ23)/7 & (โ19)/5 Since both numbers are negative, We ignore the signs. 23/7 & 19/5 Comparing these two numbers Since denominator is different, We make same Common denominator = L.C.M of 5 & 7 = 5 ร 7 = 35 So, 23/7 = 19/5 = Therefore, 115/35 < 133/35 i.e. 23/7 < 19/5 Multiplying โ1 both sides 23/7 ร โ1 < 19/5 ร โ1 (โ23)/7 > (โ19)/5 โ3 2/7 > โ3 4/5 So, โ3 ๐/๐ is greater.

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Davneet Singh

Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 10 years. He provides courses for Maths and Science at Teachoo.