A box contains n balls of which 2 are red and the rest are green. Two balls are to be selected at random one after the other from the box without replacement. If the probability of selecting 2 red balls is 1/28, find;

Question

the value of n
the probability that a red is selected followed by a green

Answer 1

for both red, we need

2/(n-2) * 1/(n-1) = 1/28
n = 8

Now you can do the other part.