Combinatorics

Question 21

A dice is thrown. Let A be the event that the number obtained is greater than 5. Let B be the event that the number obtained is less than 5. Then P (AUB) is

• 5/6
• 2/6
• 3/6
• None of these

Question 22

There are 100 students. 85 choose Math, 80 choose Physics, 75 choose Chemistry, 70 choose Biology. What is the minimum number of students choosing all 4 subjects? Assume each student chosen at least one subject.

• 15
• 10
• 5
• Data is insufficient