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


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Ex 6.4, 5 Find the number of ways of selecting 9 balls from 6 red balls, 5 white balls and 5 blue balls if each selection consists of 3 balls of each colour. 3 Red balls We have to select 3 red balls from 6 red balls Here, n = 6 &r = 3 No of ways of selecting 3 red balls = 6C3 = 6!/3!(6 −3)! = 20 3 White balls We have to select 3 white balls from 5 white balls Here, n = 5 & r = 3 No of ways of selecting 3 white balls = 5C3 = 5!/3!(5 − 3)! = 10 3 Blue balls We have to select 3 blue balls from 5 blue balls Here, n = 5 & r = 3 No of ways of selecting 3 white balls = 5C3 = 5!/3!(5 −3)! = 10 Thus, Number of ways of selecting of 3 balls of each color = (No. of ways selecting 3 red balls) × (No. of ways selecting 3 white balls) × (No. of ways selecting 3 blue balls) = 20 × 10 × 10 = 2000

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Davneet Singh

Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 14 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.