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7-47.

WALKING THE DOG

Marcus and his brother always argue about who will walk the dog. Their father wants to find a random way of deciding who will do the job. He invented a game to help them decide. Each boy will have a bag with three colored blocks in it: one yellow, one green, and one white. Each night before dinner, each boy draws a block out of his bag. If the colors match, Marcus walks the dog. If the two colors do not match, his brother walks the dog. Marcus’s father wants to be sure that the game is fair. Help him decide.

1. Make a probability tree of all of the possible combinations of draws that Marcus and his brother could make. How many possibilities are there?

• Create a probability tree with one branch for each possible choice.

1. What is the probability that the boys will draw matching blocks? Is the game fair? Justify your answer.

Compare the number of possible favorable outcomes to the total number of outcomes.