Question

A bowl contains 10 jellybeans (4 red, 1 blue, and 5 white). If you pick 3 jellybeans from the bowl at random and without replacement, what is the probability that exactly 2 will be red? Express in a common fraction.

Answer 1

possible outcomes are (R = red, N = nonred)
RRN ---- (4/10)(3/9)(6/8)= 1/10
RNR ---- same or 1/10
NRR ---- same or 1/10

so prob of 2reds, one different = 3/10

or, using combinations

C(4,2)xC(6,1)/C(10,3)
= 6x6/120 = 3/10