In a bag there are only red, blue, yellow, and white marbles.
A marble is taken at random from the bag.
The table shows the probabilities that the marble will be red or will be white.
| Colour | Red | Blue | Yellow | White |
|---|---|---|---|---|
| Probability | 0.25 | 0.15 |
The probability that the marble will be yellow is four times the probability that the marble will be blue.
There are 45 white marbles in the bag.
Work out the number of yellow marbles in the bag.
