Grade 11 · Math
Count unordered selections practice
Count selections where order does not matter.
Opening your practice adventure…
Try a sample
A group of 3 people is chosen from 10 people. Order does not matter. How many different groups are possible?
- 122
- 119
- 120
- 121
See the answer & why
120
Use combinations: 10! / (3! × 7!) = 120. Each unordered group is counted once.
A little hint: Use combinations when changing the order does not create a new group.
A teaching tip
Contrast a chosen group with an ordered lineup, then use the combination count.