Choose 2 books from 6 different books for a trip. How many choices are possible if order does not matter?
Show hints
- First count the choices for the first and second books.
- Divide 6 × 5 by 2 because order does not matter.
Show the answer and solution
Answer: 15
There are 6 × 5 = 30 ordered pairs, but each pair is counted twice. Therefore there are 30 ÷ 2 = 15 choices.