Question

a class of students was asked who had seen the movie The life of pi and who had seen the movie finding Nemo twenty students had seen at least one of these movies. 20% of the students had seen neither of these movies.
How many students were in the class?

Answer 1

Given:

Number of students that have watched at least one of the movies = 20

Percentage of students that have watched neither of the movies = 20%

To find:

Total number of students in the class.

Solution:

Let the set of students who watched "The life of pi" be A.

And the set of students who watched "Finding Nemo" be B.

And the total number of students be x.

Then number of students that did not watch any movie = 20*x / 100 = x/5

Then n(A∪B) = 20

And x - n(A∪B) = x/5

Putting the value of n(A∪B):

x - 20 = x/5

5x - 100 = x

4x = 100

x = 25

The total number of students is 25.