A bag contains 3 red counters and 5 blue counters, and one counter is taken at random. What is the probability that it is red? Give the probability as a fraction out of the total number of counters.

Explication

The bag holds 3 + 5 = 8 counters and 3 of them are red, so the draw succeeds in 3 cases out of 8. Answering 3/5 sets the red counters against the blue ones instead, but the bottom of a probability has to count everything that could be drawn, and the red counters are part of that total too.