Question

In a group of students ,75 scored first class in kannada,70 scored first class in social science and 45 scored first class in both. Find the number of students in the group.

Answer 1

Hint: Here we know that 45 students are first class in both subjects, it means they considered it twice. But we have to find the total number of students. Here we can use the Venn diagram method.

Complete step-by-step answer:

 Here the diagram shows students that scored first class in kannada, social science and both the subjects together.

But since 45 is common in both, so they need to be subtracted.
So , students scored first class in kanada only = total (of kanada)– common= 75-45=30
And students scored first class in social science only = total(of social science) – common= 70-45=25
Thus total students = students of Kanada only + students of social science only +common
                                =30 +25 +45
                                 =100

Note: Venn diagram saves your time and makes your calculations faster.
Generally students just add all the three numbers. but the question says in kanada and in social science. For instance in problem 75 have scored first class in kanada but 45 of them also got first class in social science. So 30 students are first class only in kanada.
Try to understand the difference between in kanada and only in kanada