Question

A factory produces 80 % round and 20 % square buttons. Suppose that 10 % of theround buttons and 50 % of the square buttons are red. What is the probability that arandomly selected red button is square?

Answer 1

5/9

Explanation:

Let the total number of buttons is x.

• Round buttons = 80% of x = 0.8x
• Square buttons = 0.2x

Number of red buttons:

• 0.1*0.8x + 0.5*0.2x =
• 0.08x + 0.1x =
• 0.18x

Number of red square buttons is 0.1x

Required probability:

• P = 0.1x/0.18x = 10/18 = 5/9