Ball selection: 5 red, 4 blue. Probability not red?

Explanation

• Total balls = 5 + 4 = 9, and “not red” refers to the 4 blue balls.
• So the probability is 4 out of 9, written as 4/9.
• A second route is the complement rule: P(not red) = 1 − P(red) = 1 − 5/9 = 4/9.
• Option B 5/9 is the probability of drawing a red ball, so the word “not” must be read carefully.
• The two probabilities add up to 1, which gives you a quick way to check the answer.