2006 AMC 12B Problem 7

Below is the professionally curated solution for Problem 7 of the 2006 AMC 12B, from LIVE by Po-Shen Loh. You can also try the full timed exam, view all 2006 AMC 12B solutions, or check the answer key.

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Concepts:multiplication principlearrangements with restrictions

Difficulty rating: 1180

7.

Mr. and Mrs. Lopez have two children. When they get into their family car, two people sit in the front, and the other two sit in the back. Either Mr. Lopez or Mrs. Lopez must sit in the driver's seat. How many seating arrangements are possible?

44

1212

1616

2424

4848

Solution:

The driver is one of the two parents: 22 choices.

Any of the remaining 33 people can sit in the front passenger seat, and the last 22 people fill the back in 22 orders.

The total is 232=12.2 \cdot 3 \cdot 2 = 12.

Thus, the correct answer is B.

Problem 7 in Other Years