After weeks of being a guest, I became a user! This is the problem:

I have 5 red plates and 4 blue plates. If I randomly select two plates to serve dinner on, what is the probability that they're both the same color?

I thought the answer was 28 2/5, but that was wrong. I only have one chance left. Thanks in advance!

KingJom Feb 23, 2019

#2**+1 **

don't bump please, someone will get to it and bumping doesn't help.

How can a probability be 28 2/5 ?

0 <= Pr[anything] <= 1

\(P[\text{both same color}] = \\ P[\text{2 red}]+P[\text{2 blue}] = \\ \dfrac{5}{9}\dfrac{4}{8} + \dfrac{4}{9}\dfrac{3}{8} = \\ \dfrac{20 + 12}{72} = \\ \dfrac{4}{9}\)

.Rom Feb 23, 2019