In a class, 72% students like Physics and 44% students like Chemistry. If each student likes at least one subject and there are 40 students who like both, what is the total number of students in the class?
Answer: C
Let the total number of students be T.
n(P) = 0.72T, n(C) = 0.44T.
Since each student likes at least one subject, n(P ∪ C) = T.
n(P ∩ C) = 40.
Using the formula n(P ∪ C) = n(P) + n(C) - n(P ∩ C):
T = 0.72T + 0.44T - 40
T = 1.16T - 40
40 = 1.16T - T
40 = 0.16T
T = 40 / 0.16 = 4000 / 16 = 250.