Solving combinatorial problems by listing choices
Answers are for parents and teachers.
1
List all two-digit numbers from the digits 7, 8, 9 without repetition.
78, 79, 87, 89, 97, 98
2
How many two-digit numbers can be made from 1, 2, 3 (repetition allowed)?
9
3
4 teams play one game against each other. How many games are there?
6
4
There are 3 shirts and 2 pairs of trousers. How many outfits are possible?
6
5
Why can the tree method be more convenient than plain listing?
The tree shows each stage of choice, so it is hard to leave an option out.