In a box there are red pens, blue pens and green pens.
The number of red pens is three times the number of green pens.
The number of blue pens is half the number of green pens.
Find the percentage of pens in the box that are green.
64 exam-style questions on Edexcel GCSE Maths Writing and Simplifying Ratio. Each one has a worked solution and a mark scheme showing where the marks go.