How Long Did the Husband Walk Before Meeting His Wife?

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Discussion Overview

The discussion revolves around a problem involving a husband who leaves work early and walks home, meeting his wife along the way. Participants explore the implications of their speeds and the timing of their meeting, aiming to determine how long the husband walked before meeting his wife. The scope includes mathematical reasoning and assumptions about their respective travel times.

Discussion Character

  • Mathematical reasoning
  • Exploratory
  • Debate/contested

Main Points Raised

  • One participant suggests that the wife's speed to the subway is crucial for determining how far the husband walks before meeting her, proposing that her speed is the same in both directions.
  • Another participant argues that the different speeds and distances are not important for solving the problem.
  • A participant notes that the wife must have left at her usual time since she was unaware of the husband's early departure.
  • One participant calculates that the husband walked for 55 minutes based on the timing of their meeting and the 10 minutes saved on their journey home.
  • Another participant emphasizes that the assumptions about the wife's speed being split evenly are necessary to draw conclusions about the time saved.

Areas of Agreement / Disagreement

Participants generally agree that the wife did not know the husband was leaving early and left at her usual time. However, there is disagreement regarding the importance of the different speeds and distances, as well as how to interpret the time saved in their journey.

Contextual Notes

Assumptions about the wife's speed and the implications of their meeting time are not fully resolved, leading to varying interpretations of the problem. The discussion does not reach a consensus on the significance of these factors.

LAF
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Everyday a man comes from work and get out the train, at station, at 5 PM. At the same time, everyday, his wife, driving a car, takes him and they go home.
One day, the man leaves his work early and get on the sation at 4 PM. So, he decides to go home walking. On the way home, he meets his wife, get in the car and they go home. This day, they arrive at home 10 minutes early. How many time has he walked?
 
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I think this diagram captures the essentials of what's given and what's being asked.

It shows that there are some assumptions that must be made in order to answer the question.

One assumption is that the wife's drive to the subway is as fast (slope of a) as the drive from the subway (slope of -a). Her speed to the subway affects how far home he gets before meeting her. To demonstrate this requirement, change the slope of the dotted line -the lengths of the blue lines will change.

We must know what her to-subway speed is; we can assume it's the same as to-home.


Another assumption: his wife did not know he was leaving early today, therefore she left at the same time as usual, right?
 

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Look at it from her point of view. If she gets home 10 minutes earlier than usual, then she must have met him 5 minutes earlier than usual. That would be 4:55, after he had walked for 55 minutes.
 
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I think it´s not important the different speed and distance anyway (to n from subway).
You right, his wife didn´t know!
 
jimmysnyder got it. He was very fast!
 
LAF said:
I think it´s not important the different speed and distance anyway (to n from subway).
You right, his wife didn´t know!

Jimmy's answer is quite elegant. However, it does make the two assumptions I stated.

(You can't conclude that the five minutes she saved are split evenly between coming and going unless you first assume that her speed is split evenly between coming and going.)
 
We must assume that the wife left at the time that she normally leaves, because she had no idea that the husband had arrived early. We know that the wife and husband arrived home 10 minutes earlier than usual, even though the wife left home at the regular time. For them to arrive home 10 minutes early, the wife would have had to have met up with her husband 5 minutes earlier than the time she usually meets him. (5pm). So, she met up with her husband at 4:55. 10 minutes would be saved because the wife would save the 5 minutes that would have been required to drive from the point she met her husband to the point of the station, as well as the five minutes back from the point of the station to the point she met her husband.

So, the husband usually arrives at 5pm. Today he arrives at 4pm. If the husband and wife arrive home 10 minutes earlier than usual, then the wife will meet up with the husband at 4:55, rather than 5pm. We know that the husband began his walk at 4pm, so the length of time the husband has been walking is 55 minutes.

It does not matter which numbers you plug in for the time, the result is always the same. If husband arrives usually at 4:30pm, then that means today he arrived at 3:30 pm. Wife needs to meet up with him at 4:25 pm to save the 10 minutes back and forth from point of husband to point of station. 3:30-4:25=50 minutes of walking for husband.
 

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