14.2 - Counting Pairs

Links and useful resources

• gr7's Prealgebra Course Outline START HERE<<<
• AoPS Online Textbook
• IXL Grade 7 index
• IXL Grade 8 index
• AoPS Alcumus
• IXL prealgebra practice index
• OpenSTAX Prealgebra-1 textbook

Concept summary and lesson

• How do you count things in situations where the order of the things in a group doesn't matter?

Worked examples

Media resources

• Youtube search for "How do you count things in situations where the order of the things in a group doesn't matter? "

Guided practice

• A round-robin tennis tournament consists of each player playing every other player exactly once. How many matches will be held during an 8-person round-robin tennis tournament?
• A round-robin tennis tournament consists of each player playing every other player exactly once. Find a formula for the number of matches that will be held during a $n$-person round-robin tennis tournament, where $n\ge 2$.
• Five women and four men are at a party.
  • (a) If each person shakes hands with each other person, then how many total handshakes are there?
  • (b) If no two men shake hands, but each woman shakes hands with each other person, then how many total handshakes are there?

Homework

• #hw (math) (gr7) 14.4 Counting Pairs (p. 530) 2025-04-23