In a bag there are only yellow, white, purple and orange marbles. A marble is taken at random from the bag. The table shows the probabilities that the marble will be yellow or will be orange.
| Colour | Yellow | White | Purple | Orange |
|---|---|---|---|---|
| Probability | 0.3 | 0.1 |
The probability that the marble will be white is twice the probability that the marble will be purple. There are 20 orange marbles in the bag.
Work out the number of white marbles in the bag.
Practise OCR GCSE Maths Probability with exam-style questions for Foundation and Higher tier. 100 questions, matched to the OCR GCSE Maths (J560) specification and written in the written papers style. Every question includes a full worked solution and mark scheme, so you can see where marks are awarded rather than just whether you got the answer right.