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# Permutations and Combinations Help (page 2)

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By McGraw-Hill Professional
Updated on Sep 13, 2011

#### Practice 3

How many permutations are there if you have 10 apples, taken 5 at a time in a specific order?

#### Solution 3

Use the above formula for permutations, plugging in q = 10 and r = 5:

10P5 = 10! / (10 – 5)!
= 10! / 5!
= 10 × 9 × 8 × 7 × 6
= 30,240

#### Practice 4

How many combinations are there if you have 10 apples, taken 5 at a time in no particular order?

#### Solution 4

Use the above formula for combinations, plugging in q = 10 and r = 5. We can use the formula that derives combinations based on permutations, because we already know from the previous problem that 10P5 = 30,240:

10C5 = 10P5 / 5!
= 30,240 / 120
= 252

Practice problems for these concepts can be found at:

Basics of Probability Practice Test

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