The multiplication rule of combinatorics
Answers are for parents and teachers.
1
How many outfits can be made from 5 shirts and 3 pairs of trousers?
15
2
How many two-digit codes are there from the digits 0 to 9 if digits may repeat?
100
3
In how many ways can 3 different letters be put into 3 different envelopes, one per envelope?
6
4
A phone number starts with 224 and is followed by 3 arbitrary digits. How many numbers are there?
1000
5
Using a tree diagram, list all outcomes of tossing 2 coins (heads/tails). How many outcomes are there?
4: HH, HT, TH, TT (2 · 2 = 4).