Question

An urn contains 6red,4blue,2green,and 3yellow marbles. If four marbles are picked at random,what is the probability that at least one is blue??​

Answer 1

Answer:

Total probability = P(exactly one is blue)+P(exactly two are blue) + P(exactly three at blue) + P(exactly four blue are picked)

= 4C1*11C3/15C4 (Because I want exactly one blue ball and other 11 remaining balls to be 3 in number because total four balls are to selected and hence finally dividing by 15 C 4 because that's the total number of ways in which I could have selected any four balls out of the 15 balls)

+ 4C2*11C2/15C4 + 4C3*11C1/15C4 + 4C4*11C0/15C4

So, total probability = 4C1*11C3/15C4 + 4C2*11C2/15C4 + 4C3*11C1/15C4 + 4C4*11C0/15C4

I can leave the calculation to you surely ｡◕‿◕｡, hope this helps you !