PPE Paper: 3rd Question (Economics)

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Samantha **
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Hi everyone,

I've been looking at the sample PPE paper that Oxford publish, and will copy the 3rd question here (which is roughly supposed to correspond to Economics). I have put my answers below, and I am uncertain on two. Can anybody help?

3. Each day 10,000 people must travel from A to B. They can either take the train, which always takes 40 minutes irrespective of the number of people who use it, or drive. Driving takes 20 minutes when there is no other traffic on the road, but each additionall 200 cards adds 1 minute to everyone's driving time. We assume that people make their choice of how they would like to travel solely on the basis of the expected journey time.

a. The local council decides to limit car usage and issues 2,000 free licences for the right to use the road. (1) How long will those who obtain licences take to travel? (2) How many will apply for the licences?

b. Suppose the local council decides instead that car usage should be unrestricted. (1) Will everybody choose to try travelling by car? Eventually, the number of cars on the road adjusts to make the travelling time by car equal to the travelling time by train. (2) In this case, how many people are choosing to drive? (3) What is the percentage of the population who chooses to travel by train?

My answers:

a. (1)
2,000 / 200 = 10 extra minutes
20 minutes + 10 minutes = 30 minutes travelling time

a. (2) UNSURE?
The journey time can only ever be 30 minutes, as only 2,000 licences are given out, so travellers who successfully obtain a licence will always make there journey in 30 minutes - 10 less than by train. Therefore, all 10,000 people will apply, as if they are successful, their journey time will be reduced by 10 minutes. IS THIS RIGHT?

b. (1) UNSURE?
If all 10,000 travellers decided to travel by car, the journey time would be 50 minutes (10,000 / 200 = 50). 50 minutes is ten minutes longer than the 40 minutes guaranteed by train travel. 4,000 is the maximum number of car users that will allow the road travelling time to be equal to the train travelling time (20 minutes extra = 20 x 200 = 4,000). If more than 4,000 people use cars, their journey time will be increased, and people will obviously be aware of this. All 10,000 travellers could assume there's a reasonable chance that their driving will be less than or equal to train travelling time (a 2:3 chance - 4,000 people to 6,000 people), and so all might decide to travel by car. However, all 10,000 travellers might be aware that the final 6,000 people will make the car journey time longer than the train journey time, and so might decide to go by train, as some people must do. The answer is therefore inconclusive, but what does seem obvious is that the number of people that decide to use the road will even out in the end, so that 4,000 or less are driving, and 6,000 or more are using the train. IS THIS IN ANY WAY RIGHT? I CANNOT SEEM TO REACH A CONCLUSION. CAN ANYONE ELSE? IS PROBABILITY NEEDED?

b. (2)

1 minute more than 20 minutes (the standard time without traffic) is because of 200 extra people.
There are 20 extra minutes in the 40 minute journey time (40 - 20 = 20).
1 extra min = 200 extra people, so 20 extra minutes = 20 x 200 = 4,000 people.

c. (3)
4,000 / 10,000 = 0.4
0.4 x 100 = 40%

Thanks everybody. Any help would be appreciated.
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llama boy
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The key is I think, that if you make any assumptions, make it absolutely clear what they are.

I'm not going to look at your answers as I've yet to do it properly myself.
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Linda
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Sam, do you do maths?
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Samantha **
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Is this T2U Linda? If so, *hi*!

Nope, I stopped Maths at GCSE. Which is why I am anxious about Economics.
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Linda
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(Original post by Samantha **)
Is this T2U Linda? If so, *hi*!

Nope, I stopped Maths at GCSE. Which is why I am anxious about Economics.
Yes, it's me. If you don't do maths I'm sure your way of reasoning is just fine. For those who do maths however i think you should show it mathematically rather than verbally and derive equations (such as 40=20+(x/200) for #2b, where x is number of people driving).
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Sam-jones
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I got the same answers as you for all but the last question. For that I got 60% - think you did 4000/10000 times 100 where as i did 6000/10000.
Where did you find the test?
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Linda
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(Original post by Sam-jones)
I got the same answers as you for all but the last question. For that I got 60% - think you did 4000/10000 times 100 where as i did 6000/10000.
Where did you find the test?
Yeah, 40% go by car, 60% by train. The test is from oxford's website.
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Samantha **
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Yes - I read the question wrong! And it's not 50 minutes if they all went by car, it's 70 minutes - I forgot to add it to the 20 minutes without traffic. Oh gosh, such stupid mistakes! At least I'm making them now. []
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Linda
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Hey Sam, what did you write on number 1 -if the views could be reconciled?
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Sam-jones
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(Original post by Linda)
Hey Sam, what did you write on number 1 -if the views could be reconciled?
Hey,
For b (1)
The equation for the time taken to travel by car: t = (x/200) + 20 (where t = time taken and x = the number of additional passengers.
(t = 40 when x = 4000) therefore, we have equilibrium when the number of passengers travelling by road is 4000.
Hey,
For b (1)
The equation for the time taken to travel by car: t = (x/200) + 20 (where t = time taken and x = the number of additional passengers.
(t = 40 when x = 4000) therefore, we have equilibrium when the number of passengers travelling by road is 4000.

Going back to the original question, we are told to assume that people make their choice of how they would like to travel solely on the basis of the expected journey time. If there is ‘perfect knowledge’ then I would say that only the first 4000 would travel by car. However is there is imperfect knowledge (which is far more likely) then I would say that the full 10000 would try to travel by car. This would only happen on one occasion.

Basically I have reached the same conclusion as Samantha – ‘‘the answer is therefore inconclusive, but what does seem obvious is that the number of people that decide to use the road will even out in the end, so that 4,000 or less are driving, and 6,000 or more are using the train.’’

Linda what subject have you applied for, I have gone for Land Economy at Cambridge.
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Linda
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(Original post by Sam-jones)
Hey,
For b (1)
The equation for the time taken to travel by car: t = (x/200) + 20 (where t = time taken and x = the number of additional passengers.
(t = 40 when x = 4000) therefore, we have equilibrium when the number of passengers travelling by road is 4000.
Hey,
For b (1)
The equation for the time taken to travel by car: t = (x/200) + 20 (where t = time taken and x = the number of additional passengers.
(t = 40 when x = 4000) therefore, we have equilibrium when the number of passengers travelling by road is 4000.

Going back to the original question, we are told to assume that people make their choice of how they would like to travel solely on the basis of the expected journey time. If there is ‘perfect knowledge’ then I would say that only the first 4000 would travel by car. However is there is imperfect knowledge (which is far more likely) then I would say that the full 10000 would try to travel by car. This would only happen on one occasion.

Basically I have reached the same conclusion as Samantha – ‘‘the answer is therefore inconclusive, but what does seem obvious is that the number of people that decide to use the road will even out in the end, so that 4,000 or less are driving, and 6,000 or more are using the train.’’

Linda what subject have you applied for, I have gone for Land Economy at Cambridge.
I meant #1 on the paper, deals with politics and science. There's a passage written by Mao I'm not sure I understand. Thanks anyways.

I've applied for PPE at Teddy Hall (Oxford).

Btw, in your equation x is the number of total passangers going by car.
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Sam-jones
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(Original post by Linda)
I meant #1 on the paper, deals with politics and science. There's a passage written by Mao I'm not sure I understand. Thanks anyways.

I've applied for PPE at Teddy Hall (Oxford).

Btw, in your equation x is the number of total passangers going by car.
Gotcha,
What did you write?
I am just looking at the test now. The second question is not very nice, but it does make you think. What did you put?
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Linda
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Well, I haven't really answered it. At first thought it seems as though they couldn't, because Mao says one should use science in political pursuits, while Carey is talknig about how science and politics should not interfere. But then again, one might even say that the to views cannot be reconciled because they are talking about to differnt things alltogether (how politics obscure science and how science can be used in politics).
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Linda
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(Original post by Linda)
Well, I haven't really answered it. At first thought it seems as though they couldn't, because Mao says one should use science in political pursuits, while Carey is talknig about how science and politics should not interfere. But then again, one might even say that the to views cannot be reconciled because they are talking about to differnt things alltogether (how politics obscure science and how science can be used in politics).
Actually, Carey is criticising the way Mao attempts to use science for political gains. Their disagreement lies in the very nature of science.
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Amrad
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Can someone link me to the paper

Thanks
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RxB
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The key assumption you need to state is that only one person can fit in a car. If you talk about carpooling it means that everyone can get there by car, more quickly.
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