Maria walked along a track at an average speed of 100 meters per

Question

Maria walked along a track at an average speed of 100 meters per minute. Was the length greater than half a kilometer?

(1) She took more than 250 seconds to cover the track
(2) She took less than 290 seconds to cover the track

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paragw · Answer

Maria's average speed is 100 meters per minute. The question asks if the length of the track she walked is greater than 500 meters.

Statement 1:  
She took more than 250 seconds to cover the track.
At minimum, that's 251 seconds.
Length = (100 × 251)/60 ≈ 418.3 meters, which is not more than 500 meters.
This statement is  Not Sufficient
 
 Statement 2:  
She took less than 290 seconds to cover the track.
At maximum, that's 289 seconds.
Length = (100 × 289)/60 ≈ 481.7 meters
Maximum distance she can travel in the given time is 481.7 meters which is less than 500 meters
Therefore,  the length was smaller than half a kilometer
Hence,  B

Dereno · Answer

Given that, average speed = (100/60) m/s

We need to find :  Is d > 500m ?

Speed = Distance / Time

(100/60) = d / Time

Time = (d * 60)/100

Assuming d minimum to be 500, then time is

Time = (500*60)/100

= 300 seconds.

As time is proportional to distance, as distance increases , time increases.

Statement 1:

(1) She took more than 250 seconds to cover the track

More than 250 seconds , falls within 300 secs as well as above 300 seconds.

Case 1: time is between (251-300) seconds, we can be sure to say, distance is less than 500 metres. Hence,  NO

Case 2: If time is above 300 secs, then distance is greater than 500 metres. Hence,  YES

Hence,  Insufficient

Statement 2:

(2) She took less than 290 seconds to cover the track.

Given that time is less than 290 seconds, which is below 300 seconds.

Thus, we can concretely say that the distance traveled is not greater than 500 metres.

Hence ,  Sufficient

Option B

RohanNewDelhi · Answer

in the question they have asked about the length it could have been how much maria had walked? could have been 2-3 rounds shouldn't the answer be E?

egmat · Answer

Hi RohanNewDelhi,

I see exactly where the worry is coming from, and it's worth untangling.

The question isn't asking  how far Maria walked in total  - it's asking about  the length of the track , a fixed distance. And both statements time how long she took  to cover the track , i.e. to walk that one length once. So laps never enter the picture: the time given is the time for a single traversal of the track, which pins the length directly.

Here's the anchor the thread already set up. At  100  meters per minute, walking exactly  500  meters (half a kilometer) would take:

500  / ( 100 / 60 ) =  300  seconds.

So the whole question reduces to: was her time above or below  300  seconds?

Statement (2):  she took  less than 290  seconds. Since  290  is already under  300 , any time below it gives a length under  500  meters - a definite  No . One clear answer every time, so  sufficient .

Now the two-case check that makes (1) fail - the move that matters in DS:

- t =  251  s -> length ~  418  m -> No
- t =  350  s -> length ~  583  m -> Yes

Same statement, two different answers ->  not sufficient . That's why it's not E: E would require statement (2) to also leave two answers open, but it doesn't - it locks the length under  500  by itself.

The takeaway: when a statement allows two valid cases with different answers it's  not sufficient ; when every allowed case lands on the same answer, it is.

Answer: B

Maria walked along a track at an average speed of 100 meters per

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GMAT Data Sufficiency (DS) Questions

Maria walked along a track at an average speed of 100 meters per

Prep Toolkit

615 to 715 in 15 Days (Ria's Strategies)

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