How to count combinations of things
When you have a question like “How many ways…?”
- SYSTEMATIC listing can help in simple cases
- Write down the thing you are counting with “AND”s and “OR”s
- Remember that (like in Probability problems):
“AND means ×”
“OR means +”
- Beware of REPETITIONS and whether they are allowed or not
(If they are not we reduce the number of options by one)
Edexcel GCSE Maths Notes
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