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14 Aug 2019, 01:31
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C
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
15%
(low)
Question Stats:
76% (01:21) correct
24%
(01:19)
wrong
based on 178
sessions
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If Runner A followed Runner B down a portion of track that is 1/3 mile long, how many seconds did it take Runner A to run the track?
(1) Runner A ran onto the track 10 seconds after Runner B ran onto the track and ran off the track 8 seconds after Runner B ran off the track.
(2) Runner B ran the track at a constant speed of 9 miles per hour.
(1) Runner A ran onto the track 10 seconds after Runner B ran onto the track and ran off the track 8 seconds after Runner B ran off the track.
(2) Runner B ran the track at a constant speed of 9 miles per hour.
19 Aug 2019, 08:14
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The problem doesn't give any extra condition, however it gives a data point which is the distance run by runner A and runner B ---> ea = eb = 1/3 miles
we need to find out ta (time taken by runner A to complete the 1/3 miles)
(1) ta = tb - 10 + 8 (Runner A entered the track 10 seconds after Runner B, which means that time for runner A to complete the track is 10 seconds less than the time taken by Runner B). In addition, Runner A finished the track after 8 seconds Runner B finished, whcih means that the time for runner A to complete the track is 8 seconds more than the time taken by Runner B
we can't find out ta cause we don't have tb
INSUFFICIENT
(2) vb = eb/tb ---> 9 = 0.33/tb ---> tb = 1/27 seconds
ta is not even in the equation
INSUFFICIENT
But if we consider both equations, we have the soution for tb in (2), which is the value we were missing in (1) to find out the value for ta
(1) and (2) TOGETHER ---> SUFFICIENT
OPTION C
Please hit the kudos button if this solution helped you
we need to find out ta (time taken by runner A to complete the 1/3 miles)
(1) ta = tb - 10 + 8 (Runner A entered the track 10 seconds after Runner B, which means that time for runner A to complete the track is 10 seconds less than the time taken by Runner B). In addition, Runner A finished the track after 8 seconds Runner B finished, whcih means that the time for runner A to complete the track is 8 seconds more than the time taken by Runner B
we can't find out ta cause we don't have tb
INSUFFICIENT
(2) vb = eb/tb ---> 9 = 0.33/tb ---> tb = 1/27 seconds
ta is not even in the equation
INSUFFICIENT
But if we consider both equations, we have the soution for tb in (2), which is the value we were missing in (1) to find out the value for ta
(1) and (2) TOGETHER ---> SUFFICIENT
OPTION C
Please hit the kudos button if this solution helped you
10 Sep 2019, 02:26
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Bunuel
Official Explanation
We have a speed problem here, so we may be working with the equation, speed = distance/time. But we also have a comparison. So, on one hand, we might be able to answer this information by getting complete information; on the other, we might be able to answer it with information that isn't complete, but which has the right comparative information. On to the data statements, which we first look at separately. Statement (1) defines the time Runner A took to run the track in terms of the time it took Runner B. But we don't know that latter quantity, so Statement (1) is insufficient. Next we look at Statement (2) alone. It gives us Runner B's speed, which allows us to calculate Runner B's time based on the length of the track. But when we look at Statement (2) alone, we have no information about how to relate this knowledge about Runner B to Runner A. So Statement (2) is insufficient. Combining the statements, we have what we need: Runner A's time in terms of Runner B's time, and Runner B's time. So the statements are sufficient together.
The correct answer is (C).
