Question 129 Problem Solving 2018 GMAT Official Guide

Question 129 Problem Solving 2018 GMAT Official Guide

Video explanation: After driving to a riverfront parking lot, Bob plans to run south…

Comments

Jayita Ghoshsays

Hi,

I have a confusion with regards to the actual question.

Question states:

After running 3.25 miles south, he decides to run
for only 50 minutes more. If Bob runs at a constant rate of 8 minutes per mile, how many miles farther south can he run and still be able to return to the parking lot in 50 minutes?

I thought this meant, he ran 3.25 miles, then he ran 50 more minutes at the rate of 1/8 mile per minute(ie 6.25miles), then another d miles south (because the question says how many miles “FURTHER” can he run south).

so, I solved the question by :

Distance= 3.25 + 6.25 + d +d
time= 50 mins
speed= 1/8 mile /minute

and now find d.

where am I going wrong? The wording of the question stem is not clear. Please help

It is a hard question, but the wording is precise. Once Bob is 3.25 miles south of the parking lot, he decides to run for a total of an additional 50 minutes from that point. And in that 50 minutes time, he needs to be back to where he started, which is the parking lot that is 3.25 miles north.

So once the 50 minute timer starts, he needs to run south, and at some point turn around and be back to his original starting point, which is the parking lot. This is what the problem statement is saying. Does this make sense?

You are treating the 50 minutes as the additional time that he runs past the 3.25 miles south marker, but the 50 minutes is the total time that he has to run south, and at some point turn around and then be back to the starting point.

I hope this makes sense. It is always harder to write in words to convey the meaning.

I approached the question differently. I managed the correct answer, but I would appreciate it if you can tell if my assumption is correct.

So what I have done is that I calculated the distance that Bob can run in 50 minutes and that is 1mile/8 min * 50 min = 6.25 miles
Since he already run 3.25 miles, then the total distance that Bob will cover is 3.25 + 6.25 = 9.5 miles

Bob will run the same distance south as he will be running north. As a result, Bob will run 9.5/2 = 4.75 south and 4.75 north.

Since he ran 3.25 miles south, the further distance south he can run is 4.75 – 3.25 = 1.5 miles.

Jayita Ghosh says

Hi,

I have a confusion with regards to the actual question.

Question states:

After running 3.25 miles south, he decides to run

for only 50 minutes more. If Bob runs at a constant rate of 8 minutes per mile, how many miles farther south can he run and still be able to return to the parking lot in 50 minutes?

I thought this meant, he ran 3.25 miles, then he ran 50 more minutes at the rate of 1/8 mile per minute(ie 6.25miles), then another d miles south (because the question says how many miles “FURTHER” can he run south).

so, I solved the question by :

Distance= 3.25 + 6.25 + d +d

time= 50 mins

speed= 1/8 mile /minute

and now find d.

where am I going wrong? The wording of the question stem is not clear. Please help

Thank you

GMAT Quantum says

Hi Jayita,

It is a hard question, but the wording is precise. Once Bob is 3.25 miles south of the parking lot, he decides to run for a total of an additional 50 minutes from that point. And in that 50 minutes time, he needs to be back to where he started, which is the parking lot that is 3.25 miles north.

So once the 50 minute timer starts, he needs to run south, and at some point turn around and be back to his original starting point, which is the parking lot. This is what the problem statement is saying. Does this make sense?

You are treating the 50 minutes as the additional time that he runs past the 3.25 miles south marker, but the 50 minutes is the total time that he has to run south, and at some point turn around and then be back to the starting point.

I hope this makes sense. It is always harder to write in words to convey the meaning.

Dabral

Yousef says

Hey,

I approached the question differently. I managed the correct answer, but I would appreciate it if you can tell if my assumption is correct.

So what I have done is that I calculated the distance that Bob can run in 50 minutes and that is 1mile/8 min * 50 min = 6.25 miles

Since he already run 3.25 miles, then the total distance that Bob will cover is 3.25 + 6.25 = 9.5 miles

Bob will run the same distance south as he will be running north. As a result, Bob will run 9.5/2 = 4.75 south and 4.75 north.

Since he ran 3.25 miles south, the further distance south he can run is 4.75 – 3.25 = 1.5 miles.

Is this approach correct?

GMAT Quantum says

Hi Youssef,

This is perfect, I like your approach.

Dabral