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jmc

prealgebra junior

Problem

Each of the twenty dots on the graph below represents one of Sarah's classmates. Classmates who are friends are connected with a line segment. For her birthday party, Sarah is inviting only the following: all of her friends and all of those classmates who are friends with at least one of her friends. How many classmates will not be invited to Sarah's party?
problem
(A)
(B)
(C)
(D)
Solution
There are people who are friends with only each other who won't be invited, plus person who has no friends, and people who are friends of friends of friends who won't be invited. So the answer is .
Final answer
D