In a class,30 students passed in math,20 passed in physics and 8 passed in both. How many students failed in both if the class has 45 students?

the number who passed either or both is

30+20-8 = 42

so, ...

43

To find out how many students failed in both math and physics, we need to subtract the number of students who passed in both subjects from the total number of students.

Total number of students = 45
Students passed in math = 30
Students passed in physics = 20
Students passed in both math and physics = 8

First, let's find the number of students who passed in either math or physics:

Students passed in either math or physics = Students passed in math + Students passed in physics - Students passed in both
Students passed in either math or physics = 30 + 20 - 8 = 42

Now, let's find the number of students who failed in both math and physics:

Students failed in both math and physics = Total number of students - Students passed in either math or physics
Students failed in both math and physics = 45 - 42 = 3

Therefore, 3 students failed in both math and physics.

To find the number of students who failed in both math and physics, we need to subtract the number of students who passed in both subjects from the total number of students.

First, let's find the number of students who passed in either math or physics. We can do this by adding the number of students who passed in math to the number of students who passed in physics and then subtracting the number of students who passed in both subjects (to avoid double-counting).

Number of students who passed in either math or physics = Number of students who passed in math + Number of students who passed in physics - Number of students who passed in both

Number of students who passed in either math or physics = 30 + 20 - 8 = 42

Now, let's find the number of students who failed in both subjects. We can do this by subtracting the number of students who passed in either math or physics from the total number of students in the class.

Number of students who failed in both math and physics = Total number of students - Number of students who passed in either math or physics

Number of students who failed in both math and physics = 45 - 42 = 3

Therefore, 3 students failed in both math and physics.