William's marbles

Probability Level 1

There are 20 marbles in a bag. Ten of the marbles are red, 6 are blue, and 4 are green. What is the least amount of marbles William will need to pick out of the bag to be sure he has 2 blue marbles?

16 20 2 6

2 solutions

Mr. India
Mar 25, 2019

Taking the worst case that we never get a blue marble,

We first get all non-blue marbles that is $14$ $(10+4)$

Then only blue are left and to get $2$ of them we have to take out $\boxed{\boxed{16}}$ marbles

William Feung
Mar 25, 2019

For this problem you basically find the worst possibility, like if you were the most unlucky person in the world you would pull out 10 red marbles ten there would not be any more red marbles, then next you pull out 4 green marbles and now all that you are left with are the blue marbles so now you pull out two marbles and they must be blue. So 10+4+2=16.

William's marbles

2 solutions

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