An athlete runs R miles in H hours, then rides a bike Q miles in the same number of hours. Which of the following represents the average speed, in miles per hour, for these two activities combined?
(A) (R-Q)/H
(B) (R-Q)/2H
(C) [2(R+Q)]/H
(D) [2(R+Q)]/2H
(E) (R+Q)/2H
The OA is E.
I'm confused with this PS question. Experts, any suggestion? I'm not sure about how can I solve. I know that the average speed should be, total distance/total time, right? Thanks in advance.
An athlete runs R miles in H hours...
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Hello LUANDATO.
Let's take a look at your question.
R miles in H hours implies R/H miles per hour.
Q miles in H hours implies Q/H miles per hour.
Then, the combined average speed is equal to $$\frac{\frac{R}{H}+\frac{Q}{H}}{2}=\frac{R+Q}{2H}.$$
This is why the correct answer is the option E.
I hope this explanation can help you.
Feel free to ask me again if you have a doubt.
Regards.
Let's take a look at your question.
R miles in H hours implies R/H miles per hour.
Q miles in H hours implies Q/H miles per hour.
Then, the combined average speed is equal to $$\frac{\frac{R}{H}+\frac{Q}{H}}{2}=\frac{R+Q}{2H}.$$
This is why the correct answer is the option E.
I hope this explanation can help you.
Feel free to ask me again if you have a doubt.
Regards.
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We need to determine average speed:LUANDATO wrote:An athlete runs R miles in H hours, then rides a bike Q miles in the same number of hours. Which of the following represents the average speed, in miles per hour, for these two activities combined?
(A) (R-Q)/H
(B) (R-Q)/2H
(C) [2(R+Q)]/H
(D) [2(R+Q)]/2H
(E) (R+Q)/2H
average speed = total distance/total time
average = (R + Q)/(H + H) = (R + Q)/2H
Answer: E
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Hi LUANDATO,
As far as story problems go, this one is fairly easy from a "logic" standpoint. You can also solve it by TESTing VALUES.
R = 4
H = 2
Q = 6
So the athlete runs 4 miles in 2 hours, then bikes 6 miles in another 2 hours.
Total Distance = 4+6 = 10 miles
Total Time = 2+2 = 4 hours
Average speed = 10/4 = 2.5 miles/hr.
Plugging these values into the answer choices gives us just one match...
Final Answer: E
GMAT assassins aren't born, they're made,
Rich
As far as story problems go, this one is fairly easy from a "logic" standpoint. You can also solve it by TESTing VALUES.
R = 4
H = 2
Q = 6
So the athlete runs 4 miles in 2 hours, then bikes 6 miles in another 2 hours.
Total Distance = 4+6 = 10 miles
Total Time = 2+2 = 4 hours
Average speed = 10/4 = 2.5 miles/hr.
Plugging these values into the answer choices gives us just one match...
Final Answer: E
GMAT assassins aren't born, they're made,
Rich