GMAT Math : Calculating rate
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Example Questions
Example Question #231 : Word Problems
Randall traveled 75 kilometers in 600 minutes. What was Randall's per hour rate?
We need to pay close attention to some details here.
1) We are given time in minutes, but asked for an answer in hours.
2) A rate can be defined as distance over time.
Taking the first detail, we convert 600 minutes to 10 hours, since there are 60 minutes in one hour.
Taking the second detail, we divide 75 kilometers by 10 hours. This gives us an answer of 7.5 kilometers per hour.
Example Question #231 : Word Problems
Ray travels 
If Ray covers 
Perform the following calculation to find how long it takes to cover 
Example Question #233 : Word Problems
If a plane flies the 3000 miles from San Francisco to New York at an average speed of 600 mph, and then, buffetted by a hefty headwind, makes the return trip at an average speed of 300 mph. What was its average speed over the entire round trip?
In combined rate problems such as this, we must first find units of the desired answer: 
To find total hours, we just have to use each leg's speed:
The trip therefore took 15 total hours.
Now we simply divide the totals to find the average speed:
Example Question #11 : Rate Problems
Frank can eat a huckleberry pie in 15 minutes. His formidable sister, Francine, can eat it in 10 minutes. How long does it take them to eat a pie together?
5 minutes
6 minutes
8 minutes
25 minutes
12.5 minutes
6 minutes
To solve this combined rate problem, we must use the equation:
Where A and B are the times it takes Frank and Francine, respectively, to eat a pie.
Therefore, it takes Frank and Francine
to eat the pie.
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