There are 30 pens in a box. 12 of the pens are black. 7 of the pens are green. The probability that the pen is red is 1130\displaystyle \frac{11}{30}3011. One of the pens is chosen at random.
Find the number of pens that are red.
236 exam-style questions on AQA GCSE Maths Probability. Each one has a worked solution and a mark scheme showing where the marks go.