GMAT Quantitative Reasoning Practice Test 1

Question : 90 of 100

Marks: +1, -0

The "Racing magic" takes 120 seconds to circle the racing track once. The "Charging bull" makes 40 rounds of the track in an hour. If they left the starting point together, how many minutes will it take for them to meet at the starting point for the second time?

Validate

Solution:

The rate of the “racing magic” is 40 rounds per hour, or 1 round every 1.5 minutes. The rate of the “Charging bull” is 1 round every 120 seconds, or 1 round every 2 minutes.
The best way to solve such a question is to find the least common denominator between the two rates. At that point, they will meet for the first time, and when multiplied by 2 , we find the second time they meet:

1 / 2 ↔ 1 / 1.5=3 / 6 ↔ 4 / 6

. They will meet for the first time after 6 minutes and for the second time after 12 minutes.

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