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gmatmathguy123
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The amount of coal a train burns each mile is directly propo Updated on: 26 May 2014, 02:11
Originally posted by gmatmathguy123 on 04 May 2010, 06:13.
Last edited by Bunuel on 26 May 2014, 02:11, edited 2 times in total.
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78% (01:23) correct 22% (01:24) wrong based on 911 sessions

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The amount of coal a train burns each mile is directly proportional to the speed at which it travels. How much coal will it burn on this particular 60 mile trip?

(1) On a previous trip, the train burned 100 pounds of coal on a 60 mile trip at 60 miles per hour
(2) On this particular trip, the train is travelling at a speed of 30 miles per hour.


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(isn't the second statement irrelevant? because once you know the value of the constant of fuel burned per speed (directly proportional to one another so it doesnt change in value), you know the distance, and since rate and time are inversely proportional to one another, doesn't the actual rate become unimportant? The book answer to this question was C, but I don't understand why its not A...)
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C
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nverma
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The amount of coal a train burns each mile is directly propo 04 May 2010, 07:29
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gmatmathguy123
The amount of coal a train burns each mile is directly proportional to the speed at which it travels. How much coal will it burn on this particular 60 mile trip?
(1) On a previous trip, the train burned 100 pounds of coal on a 60 mile trip at 60 mph
(2) On this particular trip, the train is traveling at a speed of 30mph



(isn't the second statement irrelevant? because once you know the value of the constant of fuel burned per speed (directly proportional to one another so it doesnt change in value), you know the distance, and since rate and time are inversely proportional to one another, doesn't the actual rate become unimportant? The book answer to this question was C, but I don't understand why its not A...)
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Given C = k*M, where C is amount of coal/per mile, k proportionality constant, and M speed of the train.
So, We have to find C and distance is given as 60
To find C, we need the value of k and the speed at which present journey is made.

Statement 1:
(100/60) = k*(60).. So k is 1/36, (Old journey..!!)
Now we have k..
DO we know the value of speed during the present journey..NO. INSUFFICIENT

Statement 2:
C = k* (60/30)
We have the speed of the present journey. But don't have the value of K.INSUFFICIENT

Statement 2 and Statement 1:
For present journey, we have K and the speed.. Answer C.
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The amount of coal a train burns each mile is directly propo 16 May 2010, 12:51
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since the amount of coal the train burns is directly proportional to speed so the train burns a diffrent total amount of coal on the journey, more speed more amout of coal would be burnt, to get the fixed amount there must be a fixed speed which is provided by statement B , hence C is the right answer.
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The amount of coal a train burns each mile is directly propo 17 May 2010, 22:31
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The amount of coal a train burns each mile is directly proportional to the speed at which it travels. How much coal will it burn on this particular 60 mile trip?
(1) On a previous trip, the train burned 100 pounds of coal on a 60 mile trip at 60 mph
(2) On this particular trip, the train is traveling at a speed of 30mph


We must know the speed of the train on this particular 60 mile trip. Second statement provides speed of 30mph.
Furthermore, We must know the constant associated with the proportion. Obviously, first statement helps to find the constant.
Therefore, We need both of the statements to answer the question.
Hence, answer is C
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The amount of coal a train burns each mile is directly propo 03 Jun 2014, 09:24
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To answer the question we require to know the value of 2 parameters
1. Speed of the train
2. Rate of consumption of the coal.

From Option(1) we can only get rate of consumption of the coal. Speed of the train is unknown. Hence INSUFFICIENT
From Option(2) We only have the speed of the train. rate of consumption of coal is Unkown. Again INSUFFICIENT

Combining (1) and(2) we clearly get both the parameters

Hope This Helps
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The amount of coal a train burns each mile is directly propo 18 Jul 2016, 00:32
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Sindbad
To answer the question we require to know the value of 2 parameters
1. Speed of the train
2. Rate of consumption of the coal.

From Option(1) we can only get rate of consumption of the coal. Speed of the train is unknown. Hence INSUFFICIENT
From Option(2) We only have the speed of the train. rate of consumption of coal is Unkown. Again INSUFFICIENT

Combining (1) and(2) we clearly get both the parameters

Hope This Helps
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People implied here that => if y is proportional to x, it means y = mx .
But its actually y = mx +c . Here is the special case since if speed is 0, we are taking special condition and saying fuel consumed will be 0.
If it was anything other than speed and coal consumption question, i think that time answer should have been E.
But i am not sure of that also.. :( Can anyone please confirm it ??
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The amount of coal a train burns each mile is directly propo 13 Oct 2020, 10:52
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No calculation is needed for this question. We are told the amount of coal a train burns each mile is directly proportional to the speed at which it travels. So we will need to know the speed of the train.

(1) Tells us the amount of coal burned for a given speed. However, we do not know the speed of the train for this particular trip. Insufficient.
(2) Gives us the speed of the train. However, we do not know the proportion of coal/per mile burned. Insufficient.

(1 & 2) We have the proportionality constant and the speed of the train. Sufficient.
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The amount of coal a train burns each mile is directly propo 23 Mar 2023, 06:44
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ashutosh4018
Sindbad
To answer the question we require to know the value of 2 parameters
1. Speed of the train
2. Rate of consumption of the coal.

From Option(1) we can only get rate of consumption of the coal. Speed of the train is unknown. Hence INSUFFICIENT
From Option(2) We only have the speed of the train. rate of consumption of coal is Unkown. Again INSUFFICIENT

Combining (1) and(2) we clearly get both the parameters

Hope This Helps
People implied here that => if y is proportional to x, it means y = mx .
But its actually y = mx +c . Here is the special case since if speed is 0, we are taking special condition and saying fuel consumed will be 0.
If it was anything other than speed and coal consumption question, i think that time answer should have been E.
But i am not sure of that also.. :( Can anyone please confirm it ??
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This is nice point to note

Thank you for highlighting this point.
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The amount of coal a train burns each mile is directly propo 09 Apr 2026, 01:30
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I have a question here.

With statement 1, there is explicit mention of whether we should consider that the other metrics remain constant and we can take reference from an old journey to evaluate the performance in the new journey (ofcourse paraphrasing in other terms).

So how can we assume that statement will help in identifying the value of the constant?
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