2008 AMC 10B Problem 12

Below is the professionally curated solution for Problem 12 of the 2008 AMC 10B, from LIVE by Po-Shen Loh. You can also try the full timed exam, view all 2008 AMC 10B solutions, or check the answer key.

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Concepts:place valueunit conversionestimation

Difficulty rating: 1070

12.

Postman Pete has a pedometer to count his steps. The pedometer records up to 9999999999 steps, then flips over to 0000000000 on the next step. Pete plans to determine his mileage for a year. On January 11 Pete sets the pedometer to 00000.00000. During the year, the pedometer flips from 9999999999 to 0000000000 forty-four times. On December 3131 the pedometer reads 50000.50000. Pete takes 18001800 steps per mile. Which of the following is closest to the number of miles Pete walked during the year?

25002500

30003000

35003500

40004000

45004500

Solution:

Each flip counts 100000100000 steps, so Pete took 44100000+50000=4,450,00044\cdot 100000+50000=4{,}450{,}000 steps.

Dividing by 18001800 gives about 24722472 miles, which is closest to 2500.2500.

Thus, the correct answer is A.

Problem 12 in Other Years