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Now that you understand combinations problems and the method to solve them, there are two important combinations question types you should know.

Variation 1: Combinations from Multiple Groups
In this situation, combinations are being drawn from several groups to form a complete set. Figure out the combinations from each group and then multiply them together.

Example 10
At Sam’s Pizza Parlor, there are 8 meats, 7 vegetables, and 5 cheeses to choose from. Jonathan would like to make a pizza with 4 meats, 3 vegetables, and 3 cheeses. How many different pizzas could he order?

Solution
This problem is different from example 8. In example 8, Maria wanted to order a pizza mixing all the toppings together. In this case, Jonathan wants his pizza a specific way. But there are many ways he could have meat on his pizza, many ways he could have vegetables, and many ways he could have cheese. To answer this correctly, you need to solve each combinations problem individually and then multiply the answers together for the correct answer.

1. Do the problem as if it were a permutations problem.

GRE Probability: Simple Probability