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?
Let us assume U be the set of all students in the group
Let E be the set of students who know English
And, let H be the set of the students who know Hindi
∴ 
Given that, number of students who know Hindi n (H) = 100
Number of students who knew English, n (E) = 50
Number of students who know both, 
We have to find the total number of students in the group i.e. n (U)
∴ 
= 100 + 50 – 25
= 125
∴ Total number of students in the group = 125 students
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