A cloth bag used in a school game contains 5 red balls and 15 blue balls. Some blue balls are to be taken OUT (no ball is added) so that a ball drawn at random from the bag is then equally likely to be red or blue. How many blue balls must be taken out?

Question

Accepted Answer

10. The 5 red balls stay. If x blue balls are removed, the total becomes 20 - x, and we need 5/20 - x = 1/2, so 20 - x = 10 and x = 10. Check: 5 red and 5 blue, which is 1/2. Answer 5 removes only enough to make the counts differ by 5; 15 empties the bag of blue balls, which makes P(red) = 1, not 1/2.

A cloth bag used in a school game contains 5 red balls and 15 blue balls. Some blue balls are to be taken OUT (no ball is added) so that a ball drawn at random from the bag is then equally likely to be red or blue. How many blue balls must be taken out?

Step-by-Step Solution

Master this chapter in 30 minutes a day.

More Class 10 Probability Word Problems practice