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Vavali
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greenoak
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greenoak
It’s B.

Solution:
1) From here, we can now only now long it took to drive 200 miles. But we don’t know anything about the car’s speed during the last 200 miles; so the total time could be anything. Insufficient.

2) Let t be the time. Then, from this statement, we can obtain the equation:

400/t + 20 = 400/(t -1)

From here, we can find t, so the statement is sufficient.


your solution does not seem to work out, I get 20 = -400
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Vavali
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gmatnub
B

BTW Vavali, are you working for a test prep company? because your questions seem to be unique but varied in degrees of difficulty, some are really easy, and some are hard. It almost seem like you are using the board to test run the questions. It is odd that your math ability can vary so much.

trust me gmatnub when I tell you I am an average Joe trying to conquer this thing they call the GMAT. My maths ability has a split personality. Some days the "Genius side" decides to show(and I just seem untouchable) and on other days the "blonde side" shows up. i just hope on Test day the former shows decides to turn up.
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I'd vote for B as well!

t = 400/x ---eqn-1

t-1 = 400/(x+20) ----eqn-2

Substituting eqn1 in eqn2 and solving for t yields, t=5hrs

:arrow: So, B is sufficient
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Hi again, Vavali.

It works. See below:

400/t + 20 = 400/(t -1)

(400+20t)/t = 400/(t -1)

400t – 400 + 20t*t – 20t = 400t

20t*t – 20t – 400 = 0

t^2 – t – 20 = 0

roots 5, -4.
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Vavali
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Thanks Guys. Kudos to you all!
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Vavali
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Thanks Guys. Kudos to you all!
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vd
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B is the correct answer here
400/t + 20 = 400/(t -1)
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lexis
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400/(V+20) = 400/V -1
B IS BEST!



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