There are some green marbles and some yellow marbles in a jar.
The ratio of green marbles to yellow marbles is 4:14:14:1.
Two marbles are removed at random without replacement.
The probability that both the marbles taken are yellow is 135\displaystyle \frac{1}{35}351.
Work out how many marbles were in the jar before any marbles were removed.
Practise OCR GCSE Maths Probability Equation Questions with exam-style questions for Foundation and Higher tier. 28 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.