Question

In a group of students, 100 students know Hindi, 50 know English and 25 know both. Each of the students knows either Hindi or English. How many students are there in the group?

Answer 1

Let H = set of students, who know Hindi 

E = set of students, who know English 

Then n(H) = 100; n(E) = 50 and n(H∩E) = 25. 

∴ n(H∪E) = n(H) + n(E)-n(H∩E) 

= 100 + 50 - 25 = 125 

Hence, 125 students are there in the group.