A box contains 10 Red balls and 5 Blue balls. If two balls are selected at random without replacement then what are the chances that both balls are red?
A box contains 10 Red balls and 5 Blue balls. If two balls are selected at random without replacement then what are the chances that both balls are red?
Explanation
The probability that a red ball is drawn at random from the bag is 10/15.
Assuming the first ball was red, then the probability of picking a second red ball is now 9/14.
(You don’t need to worry about whether the first ball was blue, because if it was, both balls cannot be read, so picking a red ball first is the only probability you need to consider)
Multiply the two probabilities together and you have the combined probability of both balls being red.
10/15 * 9/14 = 90/ 210 = 3/7