Question

In a class of 40 students, 25 students like mathematics and 20 students like science. All of them like at least one subject. How many students like both mathematics and science?

• A. 10
• B. 5
• C. 15
• D. 7

Answer 1

The correct option is B 5

Let $x$ be the number of students who like both subjects.
$\Rightarrow$ Number of students who like mathematics only $=25-x$
And,
Number of students who like science only $=20-x$

$\Rightarrow$Total number of students = Number of students who like mathematics only + Number of students who like science only + Number of students who like both subjects.

$\Rightarrow$Total number of students = $(25-x)+(20-x)+x$
$\Rightarrow$Total number of students $=45-x$

And, It is given that total number of students in the class is 40.
$\Rightarrow 45-x=40\Rightarrow x=45-40=5$

So, 5 students like both subjects.
Hence, option a is correct.