Question

There are 2 green pens, 3 blue pens, 4 red pens, and 1 black pen in the teachers desk. The teacher selects 2 pens at random, and the pens are not replaced. What is the probability that the teachers will pick 2 red pens in a row?

Answer 1

2/15

Explanation:

2 green pens, 3 blue pens, 4 red pens, and 1 black pen =10 pens

P(red) = red/total = 4/10 = 2/5

Keep the pen

2 green pens, 3 blue pens, 3 red pens, and 1 black pen =9 pens

P(red) = red/total = 3/9 = 1/3

P(red,red) = 2/5 * 1/3 = 2/15