Example 24 - Chapter 1 Class 11 Sets
Last updated at Jan. 27, 2020 by Teachoo
Transcript
Example 24 In a school there are 20 teachers who teach mathematics or physics. Of these, 12 teach mathematics and 4 teach both physics and mathematics. How many teach physics ? Let M denote the set of teachers who teach mathematics and P denote the set of teachers who teach physics. The word ‘or’ means union and the word ‘and’ means intersection. Hence, Number of teachers who teach Maths or Physics = n(M ∪ P) = 20 Number of teachers who teach Maths = n(M) = 12 Number of teachers who teach Maths and physics = n(M ∩ P) = 4 Number of teachers who teach physics = n(P) = ? We know that n (M ∪ P) = n(M) + n(P) – n (M ∩ P), 20 = 12 + n(P) – 4 20 = 12 + n(P) – 4 20 = 8 + n(P) Thus n(P) = 12. Hence, 12 teachers teach physics.
Examples
Example 1
Example 2
Example 3
Example 4
Example 5 Important
Example 6 Important
Example 7
Example 8
Example 9 Important
Example 10
Example 11 Important
Example 12
Example 13 Important
Example 14
Example 15
Example 16
Example 17
Example 18 Important
Example 19
Example 20
Example 21
Example 22 Important
Example 23
Example 24 Important You are here
Example 25 Important
Example 26
Example 27 Important
Example 28
Example 29 Important
Example 30 Important
Example 31 Important
Example 32 Important
Example 33 Important
Example 34 Important
Chapter 1 Class 11 Sets
Serial order wise
About the Author
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.