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A bag holds 4 red, 7 blue and 9 green marbles.

Contributed by StemPy Lab

Try it on paper first. A hint, the key idea and the worked solution are here when you need them.

A bag holds $4$ red, $7$ blue and $9$ green marbles. One marble is taken without looking. Find $P(\text{red})$ and $P(\text{blue or green})$ .

Need a reminder? The key ideaShow

A probability is a number from 0 to 1. With equally likely outcomes, $P = \dfrac{\text{outcomes we want}}{\text{all outcomes}}$ , and $P(\text{not } A) = 1 - P(A)$ .

The worked solution

Have you tried it?

Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.

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