Question

In a group 2/5 of all students are girls and 2/3 of girls scored above 90% marks in Mathematics. If 36 girls have scored above 90%, then select the option that indicates the number of students who are not girls.
1. 54
2. 81
3. 90
4. 135

Answer 1

Correct Answer - Option 2 : 81

Given:

2/5 of all students are girls

2/3 of girls scored above 90% marks in Mathematics.

Number of girls who scored above 90% = 36

Calculation:

Let the total number of students in the group are X

So number of girls in the group = \(2 \over 5 \)X

So the number of girls who scored above 90% are \(2\over 3\)× \(2 \over 5 \)X =  \(4 \over 15 \)X

Now according to question there are 36 girls who scored more than 90 %

⇒  \(4 \over 15 \)X = 36

⇒ X = 36 ×  \(15 \over 4 \)

⇒ X = 135

So there are 135 students in the group

And number of girls in the group =  \(2 \over 5 \) × 135 = 54

⇒ The number of students who are not girl = 135 - 54 = 81

Hence, option 2 is correct.