The GMAT often includes at least one word problem that involves the rate formula. While the underlying idea is fairly simple, you can be certain that the GMAT rarely tests this concept in a straightforward manner. More often, the GMAT will challenge your knowledge of the rate equation with complex problems involving multiple objects moving at different speeds for different lengths of time. Tables are extremely useful tools to organize large quantities of complex information. Once this information is organized, the solution is not complex at all! Remember to use the standard word problem approach in with the techniques learned in this article.
The rate equation is:
Distance = rate X time
Example
Alfred and Joe left Beaverton airport at the same time and traveled in opposite directions. If Alfred traveled by train at an average rate of 185 kilometers per hour and Joe traveled by car at an average rate of 85 miles per hour, how many hours will it take Alfred and Joe to be 1,800 miles apart? (1.6 km in a mile)
- 5
- 7
- 8
- 9
- 12
Solution
- The problem is asking to solve for the number of hours it takes Alfred and Joe to travel 1,800 miles, also known as the variable t
- Assign variables. The only unknown in this equation is time, so let t = time. It is convenient to organize the information in a table
- Define mathematical relationship. Since we know the total distance, we can sum the distances that Alfred and Joe travel to equal 1,800.
- Solve
Note: don’t forget to convert units to make everything consistent. The problem gives us Alfred’s rate using kilometers per hour when we need to solve in miles per hour.
The answer is 9 hours or D.
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