Question 465 of 480
A bookseller has 30 customers buying Mathematics books, 20 buying English books, and 10 buying both. How many customers does he have altogether?
Correct Answer:
B
Explanation
Use the formula: n(M ∪ E) = n(M) + n(E) - n(M ∩ E) = 30 + 20 - 10 = 40.