passwella.
Menu

GCE Mathematics 1990 Question 15

Question 15

Sets

In a class of 80 students, every student had to study Economics or Geography, or both Economics and Geography. If 65 students studied Economics and 50 studied Geography, how many studied both subjects?

  1. A.15
  2. B.30
  3. C.35
  4. D.45
  5. E.50
Show the answer and explanation

Answer: C (35)

Explanation

n(E ∪ G) = n(E) + n(G) − n(E ∩ G), so 80 = 65 + 50 − n(E ∩ G) and n(E ∩ G) = 35.