Did it take Ann more than 2 hours to walk a distance of 10 miles along a certain trail? (1 mile = 1.6 kilometers)
1) Ann walked this distance at an average rate of less than 6.4 kilometers per hour.
2) On average, it took Ann more than 9 minutes per kilometer to walk the distance.
OA: D
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Can someone help me with this one?
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(10 miles)/(2 hours) = 5 miles per hour.fambrini wrote:Did it take Ann more than 2 hours to walk a distance of 10 miles along a certain trail? (1 mile = 1.6 kilometers)
1) Ann walked this distance at an average rate of less than 6.4 kilometers per hour.
2) On average, it took Ann more than 9 minutes per kilometer to walk the distance.
OA: D
Thus, if Ann traveled at 5 mph, it took her exactly 2 hours to travel 10 miles.
Implication:
If her speed was LESS THAN 5 MILES PER HOUR, it took her MORE THAN 2 HOURS.
(5 miles)/(1 hour) * (1.6 kilometers)/(1 mile) = 8 kilometers per hour.
Question stem, rephrased:
Was Ann's speed less than 8 kph?
Statement 1:
6.4 kph is less than 8 kph.
SUFFICIENT.
Statement 2:
(1 kilometer)/(9 minutes) * (60 minutes)/(1 hour) = 6.67 kilometers per hour.
Thus, a rate of 6.67 kph allows Ann to travel 1 kilometer in 9 minutes.
Since she took MORE than 9 minutes, her rate must have been LESS THAN 6.67 kph.
Thus, her speed was less than 8 kph.
SUFFICIENT.
The correct answer is D.
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sydneyuni2014
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Distance = Speed x Time
1) Ann always walked at an average rate of less than 6.4 km so if you refer to attached figure it will certainly take her a little over 2 hours to cover the distance (16/6 = 2.something). If she walks slower it will obviously take longer (which I included just for your reference).
Sufficient
2) Since it took Ann more than 9 min / kms so we know that average speed was at least 9 kmph or more.
Sum / No of items = Average
Sum = 16 x 9+ (+ indicates more than 9) = 144 or more mins = 2 hours and 24 mins at least.
Sufficient
1) Ann always walked at an average rate of less than 6.4 km so if you refer to attached figure it will certainly take her a little over 2 hours to cover the distance (16/6 = 2.something). If she walks slower it will obviously take longer (which I included just for your reference).
Sufficient
2) Since it took Ann more than 9 min / kms so we know that average speed was at least 9 kmph or more.
Sum / No of items = Average
Sum = 16 x 9+ (+ indicates more than 9) = 144 or more mins = 2 hours and 24 mins at least.
Sufficient
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Target question: Did it take Ann more than 2 hours to walk a distance of 10 miles?fambrini wrote:Did it take Ann more than 2 hours to walk a distance of 10 miles along a certain trail? (1 mile = 1.6 kilometers)
1) Ann walked this distance at an average rate of less than 6.4 kilometers per hour.
2) On average, it took Ann more than 9 minutes per kilometer to walk the distance.
OA: D
This is a great candidate for rephrasing the target question.
Aside: We have a video with tips on rephrasing the target question: https://www.gmatprepnow.com/module/gmat- ... cy?id=1100
If Ann were able to walk 10 miles in EXACTLY 2 hours, then Ann's average speed would EQUAL 5 miles per hour.
So, if it were to take Ann MORE THAN 2 hours, then Ann's average speed would be LESS THAN 5 miles per hour.
This means we can rephrase the target question as...
REPHRASED target question: Is Ann's average speed less than 5 miles per hour?
Since the two statements are in terms of kilometers, let's rephrase the target question one more time...
5 miles = 8 kilometers, so 5 miles per hour = 8 kilometers per hour.
RE-REPHRASED target question: Is Ann's average speed less than 8 KILOMETERS per hour?
At this point, it will be relatively easy to handle the two statements.
Statement 1: Ann walked this distance at an average rate of less than 6.4 kilometer per hour.
If Ann walked slower than 6.4 kilometer per hour, we can be CERTAIN that Ann's average speed less is than 8 kilometers per hour
Since we can answer the RE-REPHRASED target question with certainty, statement 1 is SUFFICIENT
Statement 2: On average, it took Ann more than 9 minutes per kilometer to walk this distance.
Let's see what it means for Ann to walk 1 kilometer in EXACTLY 9 minutes.
This means Ann walks 7 kilometers in 63 minutes, which means he/she walks a little SLOWER than 7 kilometers per HOUR.
Since we're told that it took Ann MORE than 9 minutes per kilometer, we can be CERTAIN that Ann's average speed less is than 8 kilometers per hour
Since we can answer the RE-REPHRASED target question with certainty, statement 2 is SUFFICIENT
Answer = D
Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
