There are only blue counters, red counters and yellow counters in a bag.
There are three times as many blue counters as yellow counters.
There are seven times as many red counters as yellow counters.
Write down the ratio of blue counters to red counters to yellow counters.
249 exam-style questions on OCR GCSE Maths Writing and Simplifying Ratio. Each one has a worked solution and a mark scheme showing where the marks go.