Question

Barbara draws pens randomly from a box containing 5 pens of the same shape and size. There is 1 green pen, 3 red pens, and 1 blue pen. She draws 1 red pen and then another red pen without replacing the first one. Find the probability of drawing 1 red pen followed by another red pen, and show the equation used. (10 points)

Answer 1

There are 5 pens total; 3 of them red.

first draw probability red: 3/5
second draw probability red: 2/4
On the second draw there is one less red pen and one less total pens because they are not being put back into the pool of pens.

combined probability red then red (without replacement)
= (3/5) * (2/4) = 6/20 = 3/10