Question

in a class of 100 students 70 takes science 60takes maths 40 study both how many students doesn't study science maths

Answer 1

n(S) = n (A) + n(B) - n(A∩B) + n(A∪B)'
100 = 70 + 60 - 40 + n(A∪B)'
n(A∪B)' = 100 - 90
n(A∪B)' = 10 students