Headline Story
Grids and Graphs, #2
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Introduction
Read the Headline Story to the students, and suggest starting with 2 friends, then 3, then 4, and keeping track in a table. You could suggest sketching “friends” as dots spaced as if around a table and “phone calls” as lines connecting the dots. Encourage students to find patterns and discuss ideas they have.
Headline Story
If 8 friends want to make the fewest phone calls so that each friend talks to every other one, how many calls will be needed?
Possible student responses
- 4 friends will make 6 calls:
- Each time a new friend joins, the new friend needs to call all the others, so eight people will need to make 6 + 4 + 5 + 6 + 7 = 28 calls.
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