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# Last year all refuse collected by Shelbyville city services was incine

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Last year all refuse collected by Shelbyville city services was incine [#permalink]

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19 Sep 2004, 05:52
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Last year all refuse collected by Shelbyville city services was incinerated. This incineration generated a large quantity of residual ash. In order to reduce the amount of residual ash Shelbyville generates this year to half of last year's total, the city has revamped its collection program. This year city services will separate for recycling enough refuse to reduce the number of truckloads of refuse to be incinerated to half of last year's number.

Which of the following is required for the revamped collection program to achieve its aim?

(A) This year, no materials that city services could separate for recycling will be incinerated.
(B) Separating recyclable materials from materials to be incinerated will cost Shelbyville less than half what it cost last year to dispose of the residual ash.
(C) Refuse collected by city services will contain a larger proportion of recyclable materials this year than it did last year.
(D) The refuse incinerated this year will generate no more residual ash per truckload incinerated than did the refuse incinerated last year.
(E) The total quantity of refuse collected by Shelbyville city service's this year will be no greater than that collected last year.

Last edited by hazelnut on 24 Jun 2017, 04:22, edited 4 times in total.

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Re: Last year all refuse collected by Shelbyville city services was incine [#permalink]

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17 Jun 2016, 01:33
Last year 10 truck had mix garbage (recyclable and non recyclable garbage)
A single truck can hold 10 Kilo of garbage==> so 10 trucks will have 100 Kilo of garbage. (10 truck X 10 KG)
lets assume that 1 Kilo of garbage produced 0.8 Kilo of ash
10 kilo of garbage (entire truck can hold 10 kilo of garbage) will produce =8 kilo of ash ==> this is amount of ash per truck
so 1 truck produces 8 Kilo of ash, therefore 10 truck will produce = 10 X 8= 80 kilo of ash

This year the aim to reduce the ash to half = 40 Kilo Ash (half of 80 kilo that was produced last year)
To achieve this only half of the truck will be burned = 5 truck out of total 10 trucks.==>(50 kilo out of 100 kilo will be burned)
1 truck will contains 10 kilo, so again 8 kg of ash will be produced==> 8 kilo of ash/per truck
but now since only half the truck will be burned , the number of truck will come down to 5 from the original 10
5 truck will produce 50 kilo garbage = 5 X 8 Kilo ash = 40 kilo of ash

What if when the composition of recyclable and non recyclable garbage is changed the amount of ash produced increases
lets say , now the ash produced per truck increases from 8 kilo to 9 kilo per truck
then even though only 5 trucks are burned the total ash will become = 5x 9 = 45 kilo of ash (which is not half of 80 kilo last year )

SO the argument is relying on the fact that the ash produced per truck will stay the same.
THIS IS THE ASSUMPTION

(D) The refuse incinerated this year will generate no more residual ash per truckload incinerated than did the refuse incinerated last year.

Last year all refuse collected by Shelbyville city services was incinerated. This incineration generated a large quantity of residual ash. In order to reduce the amount of residual ash Shelbyville generates this year to half of last year's total, the city has revamped its collection program. This year city services will separate for recycling enough refuse to reduce the number of truckloads of refuse to be incinerated to half of last year's number.

Which of the following is required for the revamped collection program to achieve its aim?

(A) This year, no materials that city services could separate for recycling will be incinerated.
(B) Separating recyclable materials from materials to be incinerated will cost Shelbyville less than half what it cost last year to dispose of the residual ash.
(C) Refuse collected by city services will contain a larger proportion of recyclable materials this year than it did last year.
(D) The refuse incinerated this year will generate no more residual ash per truckload incinerated than did the refuse incinerated last year.
(E) The total quantity of refuse collected by Shelbyville city service's this year will be no greater than that collected last year.
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Re: Last year all refuse collected by Shelbyville city services was incine [#permalink]

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04 Jul 2016, 01:28
I look this question as follow-

Whole question revolve around two step process 1. Separation 2. incineration . Question states that This year city services will separate for recycling enough refuse to reduce the number of truckloads of refuse to be incinerated to half of last year’s number - so we cannot doubt separation process . Second process we can doubt. What if incineration process has some problem and it generates less residue compared to previous year . So D

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Re: Last year all refuse collected by Shelbyville city services was incine [#permalink]

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21 Jul 2016, 01:25
maaverick wrote:
I'll go with (D)

Examining the stem:

Last year:
All refuse (collected in N truckloads) --- incinerated ---> residue ash

This year:
All refuse --- separate for recycling ---> refuse to be incinerated (resulting in half the previous year's truckloads N/2) ---- incinerate this left over refuse ----> residue ash (which is half the last year's quantity)

Therefore, this year only half the amount of residue is being incinerated. So, unless each truckload generates less residue ash than it did last year, the objective cannot be achieved.

Hi!
thanks for such good explanation but i am sorry i still don't understand what makes D right. Like C, D says that Residual will be no more than it was last year. But how can we conclude that residual will be half of what it was last year.

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Re: Last year all refuse collected by Shelbyville city services was incine [#permalink]

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21 Jul 2016, 01:39
egmat wrote:
pavan2185 wrote:
Hi ,

I am not able to get why choice D is the correct answer. I was completely stumped.

Below is my analysis.

Which of the following is required for the revamped collection program to achieve its aim?

(A) This year, no materials that city services could separate for recycling will be incinerated.

Initial thought:
Completely lost among most of the choices and chose this just for the sake of choosing an answer since I had already taken about 4 mins.

Later evaluation.

This choice says no materials will be incinerated. The target is not to completely avoid incineration. Only portion of it is to be recycled. This is not the requirement / Assumption clearly.

(B) Separating recyclable materials from materials to be incinerated will cost Shelbyville less than half what it cost last year to dispose of the residual ash.

OFS. Cost is not the concern.

(C) Refuse collected by city services will contain a larger proportion of recyclable materials this year than it did last year.

The proportion of recyclable material to refuse is relevant but not the proportion of the recyclable materials between the two years.

(D) The refuse incinerated this year will generate no more residual ash per truckload incinerated than did the refuse incinerated last year.

Initial thought: I thought the Ash per truck load is not relevant since we care about the number of truck loads of refuse to be burnt.

Later revleation.

This is the correct answer. However, is a truck load of refuse to be burnt equal to truck load of ash? I am not able to understand this properly.

(E) The total quantity of refuse collected by Shelbyville city service's this year will be no greater than that collected last year.

The total quantity is not relevant. OFS. We are concerned with the number of truck loads of trash.

Hi Pavan,

Let me explain option D with an analogy here.

Let's suppose if a doctor makes the following suggestion to you.

You need to reduce your calorie intake to half the current levels. Therefore, you should eat half as much as you currently eat. (so if you eat say 20 units, now you should eat 10 units)

Now, for the doctor's suggestion to work (i.e. reduce calorie intake to half the current levels), you should not eat, say, oily foods which contain more calories per unit. If you do that, even though you may eat only 10 units of food but your actual calorie intake will not be half of your previous level since you are eating more oily foods now which are providing you more calories per unit.

Therefore, for doctor's suggestion to achieve its aim (reduce calorie intake to half), the amount of calories per unit of food should not increase from last year.

Do you get this?

Exactly parallel is the reasoning used in option D.

You want to reduce residual ash to half the amount. What you do is that you reduce the number of trucks to half. Would that achieve the objective.

The answer is yes but only if you don't load each truck with more residual ash than the year before.

Does this help?

Thanks,
Chiranjeev

Extremely good explanation! But i still have some doubts. Here you have mentioned that to reduce the residue to half, one needs to reduce the number of trucks to 'half'. I agree, but option D says that incinerated refuse will be no longer than that of last year. now it might have reduces by 1% or 90%. How can we conclude that it reduced by 50%. Please Help!

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Re: Last year all refuse collected by Shelbyville city services was incine [#permalink]

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21 Jul 2016, 02:40
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ashutoshsh wrote:
maaverick wrote:
I'll go with (D)

Examining the stem:

Last year:
All refuse (collected in N truckloads) --- incinerated ---> residue ash

This year:
All refuse --- separate for recycling ---> refuse to be incinerated (resulting in half the previous year's truckloads N/2) ---- incinerate this left over refuse ----> residue ash (which is half the last year's quantity)

Therefore, this year only half the amount of residue is being incinerated. So, unless each truckload generates less residue ash than it did last year, the objective cannot be achieved.

Hi!
thanks for such good explanation but i am sorry i still don't understand what makes D right. Like C, D says that Residual will be no more than it was last year. But how can we conclude that residual will be half of what it was last year.

Hello, ashutoshsh

I think this question is tricky because of a lot of details that we need pay attention to.

Let's rephrase this argument and add some figures for example:

Last year we have 100 trucks with refuse
Incineration generates for example 500 tonnes (5 tonnes per truck) residual ash
In order to lessen residual ash in two times city will lessen number of trucks in two times,
so it will be 50 trucks.

But who can guarantee that residual ash from this 50 trucks will be equal to 250 tonnes (5 tonnes per truck)?

C is very close, but information that "Refuse will contain a larger proportion of recyclable materials" doesn't absolutely guaranty that this refuse will generate less volume of residual ash. It is possible and if D is not present as an answer it can be a winner,

but D is much better: "The refuse incinerated this year will generate no more residual ash per truckload" because it clearly states what we need to know.
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Re: Last year all refuse collected by Shelbyville city services was incine [#permalink]

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03 Nov 2016, 23:44
Last year all refuse collected by Shelbyville city services was incinerated. This incineration generated a large quantity of residual ash. In order to reduce the amount of residual ash Shelbyville generates this year to half of last year's total, the city has revamped its collection program. This year city services will separate for recycling enough refuse to reduce the number of truckloads of refuse to be incinerated to half of last year's number.

Which of the following is required for the revamped collection program to achieve its aim?

(A) This year, no materials that city services could separate for recycling will be incinerated.
(B) Separating recyclable materials from materials to be incinerated will cost Shelbyville less than half what it cost last year to dispose of the residual ash.
(C) Refuse collected by city services will contain a larger proportion of recyclable materials this year than it did last year.
(D) The refuse incinerated this year will generate no more residual ash per truckload incinerated than did the refuse incinerated last year.
(E) The total quantity of refuse collected by Shelbyville city service's this year will be no greater than that collected last year.

This is actually a spin off of assumption q as the word "required" signals.
When you negate, D falls apart.

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Re: Last year all refuse collected by Shelbyville city services was incine [#permalink]

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16 Nov 2016, 18:33
Here is my reasoning, somehow different from some previous explanations, and obviously open to criticism.
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Re: Last year all refuse collected by Shelbyville city services was incine [#permalink]

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19 Apr 2017, 23:37
Last year all refuse collected by Shelbyville city services was incinerated. This incineration generated a large quantity of residual ash. In order to reduce the amount of residual ash Shelbyville generates this year to half of last year's total, the city has revamped its collection program. This year city services will separate for recycling enough refuse to reduce the number of truckloads of refuse to be incinerated to half of last year's number.

Which of the following is required for the revamped collection program to achieve its aim?

(A) This year, no materials that city services could separate for recycling will be incinerated.
(B) Separating recyclable materials from materials to be incinerated will cost Shelbyville less than half what it cost last year to dispose of the residual ash.
(C) Refuse collected by city services will contain a larger proportion of recyclable materials this year than it did last year.
(D) The refuse incinerated this year will generate no more residual ash per truckload incinerated than did the refuse incinerated last year.
(E) The total quantity of refuse collected by Shelbyville city service's this year will be no greater than that collected last year.

Once you get down to C and D, you should go back and remind yourself what is the aim of the program.
The aim is to "reduce the amount of residual ash Shelbyville generates.."

In this sense, we can cross out C as we have no info of residual ash.

Hence D.

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Re: Last year all refuse collected by Shelbyville city services was incine [#permalink]

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19 May 2017, 06:03
I got it wrong!
But the key to the correct answer D is that all the premises must be true!!!
Conclusion: Reducing the ash load to 1/2 of previous year after incineration
Premises:
New program institutioned to segregate the recyclable waste so as to reduce the refuse to be incinerated to 1/2 the truck-loads.(this must be true, so C is out)
So the only way the above plan will succeed if "The refuse incinerated this year will generate no more residue ash per truckload incinerated than did the refuse incinerated last year".

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Last year all refuse collected by Shelbyville city services was incine [#permalink]

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13 Jul 2017, 18:14
Generalizing:
2016-lots of ash
2017-reduce ash by 1/2 by burning only 1/2

The most obvious assumption we can make is - what if 1/2 of the load incinerated produced the same or more ash?
Answer D questions this very assumption. By finding out the amount of ash emitted/truck load we can better understand if this plan will work.

(A) This year, no materials that city services could separate for recycling will be incinerated. - This is very extreme. 'No materials'
(B) Separating recyclable materials from materials to be incinerated will cost Shelbyville less than half what it cost last year to dispose of the residual ash.- We dont care about cost
(C) Refuse collected by city services will contain a larger proportion of recyclable materials this year than it did last year.- This can seem tempting so you can keep it to eliminate later
(D) The refuse incinerated this year will generate no more residual ash per truckload incinerated than did the refuse incinerated last year.- aw Yes! This is exactly what we assumed would happen.
(E) The total quantity of refuse collected by Shelbyville city service's this year will be no greater than that collected last year.-This does not help know whether or not halving it will produce half the ash as last year did.
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Re: Last year all refuse collected by Shelbyville city services was incine [#permalink]

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16 Jul 2017, 20:55
E is not an assumption because without E, the plan still works to make sure that the amount of ash is reduced to half by cutting the number of truckloads to half. In E, if the amout collected is greater, then recycling will do the help.

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Re: Last year all refuse collected by Shelbyville city services was incine [#permalink]

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21 Aug 2017, 02:06
I went with Option A. After that, I read all the answers here, but I am still not quite convinced with D.

The passage mentions that the refuse collected will be reduced by half of that of the previous year. This is because the remaining half will be used for recycling. Hence, if the refuse quantity is going to be half, then so is the ash from it's incineration. This will not be the case, only if the materials collected for recycling also incinerated, resulting in increased in amount of ash, which results in Answer A. However, OG has D as the answer, and the logic not quite convincing.

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Re: Last year all refuse collected by Shelbyville city services was incine [#permalink]

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21 Aug 2017, 02:38
sahilsbakshi wrote:
I went with Option A. After that, I read all the answers here, but I am still not quite convinced with D.

The passage mentions that the refuse collected will be reduced by half of that of the previous year. This is because the remaining half will be used for recycling. Hence, if the refuse quantity is going to be half, then so is the ash from it's incineration. This will not be the case, only if the materials collected for recycling also incinerated, resulting in increased in amount of ash, which results in Answer A. However, OG has D as the answer, and the logic not quite convincing.

Hi sahilsbakshi ,

This is a goal plan question in which we need to find out an option that states the plan is a good plan to achieve the goal.

Plan: Remove the recycling material from getting incinerated.
Goal: Reduce the number of truckloads of refuse to be incinerated to half of last year's number.

Option A cannot be the correct answer because it is stating what the plan is. Restatement of the plan is not a strengthener.

Option D is taking out the possibility of generating more ash out of the current residue. Hence, a strengthener.

Does that make sense?
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Re: Last year all refuse collected by Shelbyville city services was incine   [#permalink] 21 Aug 2017, 02:38

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