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GMAT Diagnostic Test Question 45 [#permalink]
07 Jun 2009, 00:13

Expert's post

GMAT Diagnostic Test Question 45 Field: algebra Difficulty: 750

Rating:

5 boxes are placed in a stack by weight from lightest to heaviest. If the heaviest box weighs \(x\) kg, then the next heaviest weighs \(x%\) less than the heaviest box. If this second-heaviest box weighs \(y\) kg, then the next heaviest weighs \(y%\) less than this second-heaviest box. And so on, for all 5 boxes. If the heaviest box weighs 10kg, approximately what percent less weight is the lightest box than the heaviest one?

A. 30 B. 40 C. 50 D. 60 E. 70

THIS QUESTION WAS REMOVED FROM THE TESTS _________________

5 boxes are placed in a stack by weight from lightest to heaviest. The heaviest box weighs \(x\) kg and then next heaviest weighs \(x%\) less than the heaviest box and the next heaviest box weighs \(x-x%\) less than the next heaviest, and so on. If the heaviest box weighs 10kg, approximately what percent less weight is the lightest box than the heaviest one?

A. 30 B. 40 C. 50 D. 60 E. 70

"The heaviest box weighs \(x\) kg and then next heaviest weighs \(x%\) less than the heaviest box" Except for the "then" typo, so far so good.

"the next heaviest box weighs \(x-x%\) less than the next heaviest" If I follow the OE, this is not written correctly. First, it shouldn't say "than the next heaviest"; it should say "than the previous heaviest box". Second, \(x-x%\) makes no sense. The OE says "The weight of the second heaviest box = x – x% of x = 10 kg – 10% of 10 kg = 9 kg". In other words, the second-heaviest box should weigh \(x - x * x%\). So the third-heaviest box should weigh \((x - x * x%)%\) less than \(x - x * x%\). Not only is this wrong, but it's way too complicated and the wording forces you to give part of the answer away.

I would simply write: If the heaviest box weighs \(x\) kg, then the next heaviest weighs \(x%\) less than the heaviest box. If this second-heaviest box weighs \(y\) kg, then the next heaviest weighs \(y%\) less than this second-heaviest box. And so on, for all 5 boxes.

Re: GMAT Diagnostic Test Question 45 [#permalink]
23 Aug 2009, 09:14

1

This post received KUDOS

bb wrote:

GMAT Diagnostic Test Question 45 Field: algebra Difficulty: 750

Rating:

5 boxes are placed in a stack by weight from lightest to heaviest. The heaviest box weighs \(x\) kg and then next heaviest weighs \(x%\) less than the heaviest box and the next heaviest box weighs \(x-x%\) less than the next heaviest, and so on. If the heaviest box weighs 10kg, approximately what percent less weight is the lightest box than the heaviest one?

A. 30 B. 40 C. 50 D. 60 E. 70

"weighs \(x-x%\) less than the next heaviest..." it's not easy to know what this sentence mean... _________________

Re: GMAT Diagnostic Test Question 45 [#permalink]
14 Jun 2009, 09:53

Explanation

Rating:

Official Answer: A

Given that the weight of the heaviest box = x kg = 10 kg The weight of the second heaviest box = x – x% of x = 10 kg – 10% of 10 kg = 9 kg The weight of the third heaviest box = 9 kg – 9% of 9 kg = 8.19 kg The weight of the fourth heaviest box = 8.19 kg – 8.19 % of 8.19 kg = 7.52kg The weight of the lightest box = 7.52 kg – 7.52% of 7.52 kg = 6.95 kg The weight of the lightest box/ the weight of the heaviest box \(= 1 - \frac{6.95}{10} \approx 30%\), which is A. _________________

Given that the weight of the heaviest box = x kg = 10 kg The weight of the second heaviest box = x – x% of x = 10 kg – 10% of 10 kg = 9 kg The weight of the third heaviest box = 9 kg – 9% of 9 kg = 8.19 kg The weight of the fourth heaviest box = 8.19 kg – 8.19 % of 8.19 kg = 7.52kg The weight of the lightest box = 7.52 kg – 7.52% of 7.52 kg = 6.95 kg The weight of the lightest box/ the weight of the heaviest box \(= 1 - \frac{6.95}{10} \approx 30%\), which is A.

Re: GMAT Diagnostic Test Question 45 [#permalink]
14 Aug 2009, 20:05

I think this question is difficult from a time consuming stand point. Once a person understands what they need to do, the person just has to crunch the numbers and get close to 3 kgs less so they know A is the correct answer. I'm thinking this is about a 650-700 question. If you really wanted to make it a 750 question (in my opinion) make it a symbolism question.

I know a lot of people that are in the upper 600s that want to break through to the low 700s and into mid-700s have a very difficult time with symbolism. _________________

------------------------------------ J Allen Morris **I'm pretty sure I'm right, but then again, I'm just a guy with his head up his a$$.

Re: GMAT Diagnostic Test Question 45 [#permalink]
14 Aug 2009, 22:46

Expert's post

jallenmorris wrote:

I think this question is difficult from a time consuming stand point. Once a person understands what they need to do, the person just has to crunch the numbers and get close to 3 kgs less so they know A is the correct answer. I'm thinking this is about a 650-700 question. If you really wanted to make it a 750 question (in my opinion) make it a symbolism question.

I know a lot of people that are in the upper 600s that want to break through to the low 700s and into mid-700s have a very difficult time with symbolism.

Thanks! By symbolism you mean "@"? _________________

Re: GMAT Diagnostic Test Question 45 [#permalink]
15 Aug 2009, 07:27

@ would work. Anything actually. The more abstract the better. I think @ is used often so it would be a good choice. Of course, you don't have to change the question, it was just a suggestion.

bb wrote:

jallenmorris wrote:

I think this question is difficult from a time consuming stand point. Once a person understands what they need to do, the person just has to crunch the numbers and get close to 3 kgs less so they know A is the correct answer. I'm thinking this is about a 650-700 question. If you really wanted to make it a 750 question (in my opinion) make it a symbolism question.

I know a lot of people that are in the upper 600s that want to break through to the low 700s and into mid-700s have a very difficult time with symbolism.

Thanks! By symbolism you mean "@"?

_________________

------------------------------------ J Allen Morris **I'm pretty sure I'm right, but then again, I'm just a guy with his head up his a$$.

Re: GMAT Diagnostic Test Question 45 [#permalink]
15 Aug 2009, 16:50

Lets make it a little polished and improved:-

bb wrote:

5 boxes are placed in a stack by weight from lightest to heaviest. The heaviest box weighs \(x\) kg and then next heaviest weighs \(x%\) less than the heaviest box and the next heaviest box weighs \(x-x%\) less than the next heaviest, and so on. Approximately what is the weight of the lightest box?

A. .3x B. .4x C. .5x D. .6x E. .7x

It is not an easy question because it, I mean the original ones as well, doesnot have any direct/quick way to get the answer. The calculation is cumbersome and time consuming. Its difficult to solve it in 2 minuets. This way it is 700+ or 750 level question.

In terms of solution, it may not be a 750 level question. _________________

Re: GMAT Diagnostic Test Question 45 [#permalink]
17 Aug 2009, 12:59

The question was a bit confusing for me: The heaviest box weighs x kg and then next heaviest weighs x% less than the heaviest box and the next heaviest box weighs x-x% less than the next heaviest, and so on.

The heaviest box( top box ) weighs x kg and then next heaviest (top-1 box )weighs x% less than the heaviest box (top box) and the next heaviest box ( top-1/top-2? box ) weighs x-x% less than the next heaviest (top-1 ? ), and so on.

Re: GMAT Diagnostic Test Question 45 [#permalink]
23 Aug 2009, 01:23

bb wrote:

5 boxes are placed in a stack by weight from lightest to heaviest. The heaviest box weighs \(x\) kg and then next heaviest weighs \(x%\) less than the heaviest box and the next heaviest box weighs \(x-x%\) less than the next heaviest, and so on. If the heaviest box weighs 10kg, approximately what percent less weight is the lightest box than the heaviest one?

I think the question is a little bid confusingly made. It says that the heaviest box weighs x kg and that the value of this box is 10 kg, which means that x is 10. Thus we subtract 10%. But then x equals 9% then 8,19... guess somewhere should be indicated that the x% equals the values of the boxes, not exactly 10 but each box and x is not stable but changes every time we move to the next box. Let me know your thoughts

Re: GMAT Diagnostic Test Question 45 [#permalink]
29 Oct 2009, 05:40

I think this question should not be on the real GMAT exam since the question itself is too confusing. I bet 90% of the people in this forum did find the expression x-x% confusing. Even someone know the concept and know what to do, it is still impossible to try to do all these calculation under 2 min without a calculator. Maybe there is another solution???

Re: GMAT Diagnostic Test Question 45 [#permalink]
17 May 2010, 05:05

I just worked on this question and x-x% also confused me. I used x as the original value (10) for all the boxes, not the previous weight. _________________