Problem 6 · 2019 Math Kangaroo
Medium
Counting & Probability
careful-counting
A park has five entrances. Monika wants to enter the park through one entrance and leave through another entrance. How many ways are there in which she can enter and leave the park?
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Answer: B — 20
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Hint 1 of 2
She enters by one entrance and leaves by a different one.
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Hint 2 of 2
Count ordered pairs of distinct entrances: 5 choices then 4.
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Approach: multiply choices for entry and exit
- There are 5 ways to choose the entrance.
- The exit must differ, leaving 4 ways.
- 5 × 4 = 20 ways.
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