Liz drove from point A to point B at 40km/h. On her way back she drove at 50km/h and therefore her way back lasted one hour less. what is the distance (in kilometers) between A and B?
A. 150.
B. 200.
C. 450.
D. 500.
E. 600.
The OA is B.
Can I say that
Distance from A to B = Speed * time = 40t
Distance from B to A = Speed * time = 50(t-1)
Then, 40t = 50(t-1) => t = 5, therefore Distance from A to B is 40*5 = 200 kilometers.
Is there a strategic approach to this question? Can any experts help? Thanks!
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Liz drove from point A to point B at 40km/h. On her way back
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Brent@GMATPrepNow
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Let's start with a word equationAAPL wrote:Liz drove from point A to point B at 40km/h. On her way back she drove at 50km/h and therefore her way back lasted one hour less. what is the distance (in kilometers) between A and B?
A. 150.
B. 200.
C. 450.
D. 500.
E. 600.
travel time at 40 kmh = travel time at 50 kmh + 1 hour
time = distances/speed
Let d = the distance from A to B
So, we get: d/40 = d/50 + 1
Multiply both sides by 200 to get: 5d = 4d + 200
Solve: d = 200
Answer: B
Cheers,
Brent
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Brent@GMATPrepNow
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Hi AAPL,AAPL wrote:Liz drove from point A to point B at 40km/h. On her way back she drove at 50km/h and therefore her way back lasted one hour less. what is the distance (in kilometers) between A and B?
A. 150.
B. 200.
C. 450.
D. 500.
E. 600.
The OA is B.
Can I say that
Distance from A to B = Speed * time = 40t
Distance from B to A = Speed * time = 50(t-1)
Then, 40t = 50(t-1) => t = 5, therefore Distance from A to B is 40*5 = 200 kilometers.
Is there a strategic approach to this question? Can any experts help? Thanks!
Your solution is perfect.
Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
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GMATGuruNY
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An alternate approach is to PLUG IN THE ANSWERS, which represent the distance.AAPL wrote:Liz drove from point A to point B at 40km/h. On her way back she drove at 50km/h and therefore her way back lasted one hour less. what is the distance (in kilometers) between A and B?
A. 150.
B. 200.
C. 450.
D. 500.
E. 600
Since the time difference yielded by the two speeds is an INTEGER VALUE -- one hour -- the correct answer is almost certain to be a multiple of the two speeds.
Of the five answer choices, only B, D and E are divisible by both 40 and 50.
When the correct answer is plugged in, the two speeds will yield a time difference of one hour.
B: 200
At a speed of 40mph, the time to travel 200 miles = d/r = 200/40 = 5 hours.
At a speed of 50mph, the time to travel 200 miles = d/r = 200/50 = 4 hours.
Time difference = 5-4 = 1 hour.
Success!
The correct answer is B.
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Followed here and elsewhere by over 1900 test-takers.
I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.
As a tutor, I don't simply teach you how I would approach problems.
I unlock the best way for YOU to solve problems.
For more information, please email me (Mitch Hunt) at [email protected].
Student Review #1
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