There are 4 green marbles and x x\,x yellow marbles in a jar.
Noah takes a marble from the jar at random.
He puts the marble back into the jar.
Noah then takes another marble at random from the jar.
The probability that the first marble Noah takes is green and the second marble Noah takes is green is 116\displaystyle \frac{1}{16}161
Work out how many yellow marbles are in the jar.
28 exam-style questions on Edexcel GCSE Maths Probability Equation Questions. Each one has a worked solution and a mark scheme showing where the marks go.