On a trolley ride around an amusement park, a child traveler

Statement A: We are not sure, Whether how much it takes for the travel- It may take 100 sec, 200 sec or even 300 sec- So Statement A is not sufficient.

Statement B: 800 meter(0.8 KM) takes less than 400. so we can say that this definitely did not take more than 400 sec- The answer to this statement is NO- Which is sufficient-

Answer is B.

Given: speed = 125m/min
Required: Distance > 0.8m?

Since both the statements are given in the form of time, it is better to convert the question in the form of time.
Distance = speed*time
(125/60)*t>800?
Or t > 384?

Statement 1: t < 450
Possible values of t:
t < 384
384 < t <450
INSUFFICIENT

Statement 2: t > 400
SUFFICIENT

Option B

Since the statements are in terms of seconds, convert the given distance -- 0.8 km -- to seconds:
\(\frac{0.8-km}{1} * \frac{1000-meters}{1-km} * \frac{1-minute}{125- meters} * \frac{60-seconds}{1-minute} = \frac{800*60}{125} = 384\) seconds.

Thus, 0.8 km is the equivalent of 384 seconds.
Implication:
To travel MORE THAN 0.8 km, the time must be MORE THAN 384 SECONDS.
Question stem, rephrased:
Is t > 384?

Statement 1: t < 450
If t = 300, the answer to the rephrased question stem is NO.
If t = 400. the answer to the rephrased question stem is YES.
Since the answer is NO in the first case but YES in the second case, INSUFFICIENT.

Statement 2: t > 400
Thus, the answer to the rephrased question stem is YES.
SUFFICIENT.

Video solution from Quant Reasoning (starts at 0:25:58):
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Just wondering if this question should have the GMAT Prep tag? I saw this question in my Official Mock 4

Added the tag. Thank you!

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