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jmc

prealgebra intermediate

Problem

Yann and Camille go to a restaurant. If there are 10 items on the menu, and each orders one dish, how many different combinations of meals can Yann and Camille order if they refuse to order the same dish? (It does matter who orders what---Yann ordering chicken and Camille ordering fish is different from Yann ordering fish and Camille ordering chicken.)
Solution
Yann can order 10 different dishes. After he has chosen a dish, Camille has 9 choices left for her dish, because she won't order the same dish as Yann did. Thus there are a total of different possible combinations of meals.
Final answer
90