2004 AMC 10A Problem 17

Below is the professionally curated solution for Problem 17 of the 2004 AMC 10A, from LIVE by Po-Shen Loh. You can also try the full timed exam, view all 2004 AMC 10A solutions, or check the answer key.

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Concepts:relative speeddistance rate and timeratio and proportion

Difficulty rating: 1540

17.

Brenda and Sally run in opposite directions on a circular track, starting at diametrically opposite points. They first meet after Brenda has run 100100 meters. They next meet after Sally has run 150150 meters past their first meeting point. Each girl runs at a constant speed. What is the length of the track in meters?

250250

300300

350350

400400

500500

Solution:

Before the first meeting the two together cover half the track. Between the first and second meetings they together cover a full track, which is twice as far, so Brenda runs 2100=2002 \cdot 100 = 200 meters in that stretch.

Sally runs 150150 meters in the same stretch, so the full track length is 200+150=350. 200 + 150 = 350.

Thus, the correct answer is C.

Problem 17 in Other Years