The probability of one event is how many ways it can happen over how many ways anything can. These free printable worksheets describe a bag of counters and ask for that chance as a fraction in its simplest form.
If they get stuck
The answer key prints on a separate page.
Two steps hide in every answer and only the second is arithmetic. First decide the whole — the total number of counters — then count the ones that count as a success, and write the second over the first. A child who counts four blue and eight red and writes 4/8 has used the reds as the whole instead of everything, and that wrong-denominator slip is the one that survives longest.
Answers simplify, so the sheet doubles as fraction practice: 4/12 is written 1/3, because a probability that is not reduced is usually not accepted. Because the answer is a fraction, these sheets stay on paper — the online pad marks a single number, and a fraction is two — while the count-prediction sheets are the part of probability that can be practiced on screen.
One question from a sheet like this one, worked a step at a time — with a sentence saying what just happened and why.
Simple probability, step by step