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A bag contains ten counters. Four of the counters are red. In an experiment three counters are taken from the bag at random and put in a box.

Calculate the probability that there are exactly two red counters in the box.

This is what I have done: $4/10*3/10= 3/25$; $2 - 3/25 = 47/25$. Is this correct? Please explain if not correct.

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    Hint: Think about what it means to have a probability greater than 1. Also, the first part of your calculation is correct, but I'm not entirely sure where you're getting the first part from. – 2017-01-29

1 Answers 1

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No, probabilities cannot be > 1. I'm not sure what you've done but you should have found the probability of taking out the bag:

Red, Red, Black 4/10 * 3/9 * 6/8 = 0.1

+

Red, Black, Red 4/10 * 6/9 * 3/8 = 0.1

+

Black, Red, Red 6/10 * 4/9 * 3/8 = 0.1

= 0.3