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How long did it take Betty to drive nonstop on a trip from

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How long did it take Betty to drive nonstop on a trip from

by BTGmoderatorLU » Wed Oct 02, 2019 12:40 am
Source: GMAT Paper Tests

How log did it take Betty to drive nonstop on a trip from home to Denver, Colorado?

1) If Betty's average speed for the trip had been \(1\frac{1}{2}\) times as fast, the trip would have taken 2 hours.
2) Betty's average speed for the trip was 50 miles per hour.

The OA is A
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Source: — Data Sufficiency |

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by Brent@GMATPrepNow » Wed Oct 02, 2019 5:16 am
BTGmoderatorLU wrote:Source: GMAT Paper Tests

How log did it take Betty to drive nonstop on a trip from home to Denver, Colorado?

1) If Betty's average speed for the trip had been \(1\frac{1}{2}\) times as fast, the trip would have taken 2 hours.
2) Betty's average speed for the trip was 50 miles per hour.

The OA is A
Target question: What was Betty's travel time?

This is a great candidate for rephrasing the target question

Let D = The distance driven
Let R = Betty's average speed

Since Time = Distance/Rate, we can rephrase the target question. . .

REPHRASED target question: What is the value of D/R?

Statement 1: If Betty's avg speed for the trip had been 1.5 times as fast, the trip would have taken 2 hours.
The distance is still the same (D), but the rate is 1.5R
So, statement 1 tells us that D/1.5R = 2
Is this enough information to find the value of D/R?
Sure, just take the equation D/1.5R = 2 and multiply both sides by 1.5 to get D/R = 3
Since we're able to answer the REPHRASED target question with certainty, statement 1 is SUFFICIENT

Statement 2: Betty's avg speed for the trip was 50 miles per hour.
This tells us that R=50
However, we cannot find the value of D/R, since we don't know the value of D (distance)
So, statement 2 is NOT SUFFICIENT

Answer: A

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
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