Author 
Message 
TAGS:

Hide Tags

Current Student
Joined: 29 Jan 2005
Posts: 5218

Machine A and machine B are each used to manufacture 660 [#permalink]
Show Tags
01 Nov 2005, 07:27
1
This post received KUDOS
5
This post was BOOKMARKED
Question Stats:
60% (04:43) correct
40% (02:24) wrong based on 122 sessions
HideShow timer Statistics
Machine A and machine B are each used to manufacture 660 sprockets. It takes machine A 10 hours longer to produce 660 sprockets than machine B. Machine B produces 10% more sprockets per hour than machine A. How many sprockets per hour does machine A produce? A. 6 B. 6.6 C. 60 D. 100 E. 110 OPEN DISCUSSION OF THIS QUESTION IS HERE: machineaandmachinebareeachusedtomanufacture98696.html
Official Answer and Stats are available only to registered users. Register/ Login.
Last edited by Bunuel on 30 Aug 2013, 04:16, edited 2 times in total.
Added the OA.



VP
Joined: 22 Aug 2005
Posts: 1112
Location: CA

B 6.6
Let A produces x sprockets per hour
therefore, B produces 1.1x sprockets (> 10%)
information given:
660/x  660/1.1x = 10
solve for x = 6
B produces 6 * 1.1 = 6.6 sprockets



SVP
Joined: 05 Apr 2005
Posts: 1710

Re: PS Rates Kap800 [#permalink]
Show Tags
01 Nov 2005, 07:53
1
This post received KUDOS
1
This post was BOOKMARKED
time taken by B = t
time taken by A = t+10
qty produced by A = q
qty produced by B = 1.1 q
for B: t(1.1q) =660
qt=600
for A: (t+10)(q) = 660
qt+10q=660
600+10q=660
q=6
so A can produce 6/hour.
then B can produce = 6(1.1)=6.6/hour.



Current Student
Joined: 28 Dec 2004
Posts: 3357
Location: New York City
Schools: Wharton'11 HBS'12

first of all those who say its 6...read the question it is asking rate of machine B
(1)660=Ra(t+10)<machine A
(2)660=1.1RaT <Machine B
I am just going to right 1.1 as 110/100
660=Rat + 10Ra (1)
RaT=660*100/110=600 (2)
660=600+10Ra; 60=10Ra; Ra=6 if Ra=6 then Rb=1.1(6)=6.6
Kapish...I dont know what work formula you guys are using....dont just post an answer...show your steps...so we can follow what you are doing...



Director
Joined: 21 Aug 2005
Posts: 789

In 1 hr, B produces > 660/B sprockets
In 1 hr, A produces > 660/(B+10) sprockets
Given,
1.1*(# produced by A) = # produced by B
1.1*660/(B+10) = 660/B > 1.1B = B + 10
=> B = 100
So,
In 1 hr, B produces > 660/100 = 6.6 sprockets



Current Student
Joined: 29 Jan 2005
Posts: 5218

1
This post received KUDOS
OE from Kaplan 800 (verbatem)
This is a very difficult rate problem, and the best approach is backsolving. Start with the middle choice (C). If machine A produces 60 sprockets per hour, then machine B produces 60 plus 10% of 60, or 66 sprockets per hour. According to the rate formula, the amount of work done, divided by the rate at which it is done, equals the time it takes to do the work. So it takes machine A 660/60, or 11 hours, while it takes machine B 660/66, or 10 hours. It doesn`t take machine A 10 hours longer than machine B at these rates, so choice (C) is out. At a slower rate it will take both machines longer, so try a smaller answer choice. Choice (A) is an interger, so it will be easier to work with than choice (B). If machine A produces 6 sprockets per hour, then machine B produces 6 plus 10% of 6, or 6.6 sprockets per hour. At these rates it takes machine A 660/6, or 110 hours, while it takes machine B 660/6.6, or 100 hours. Since in this case it does take machine A 10 hours longer than machine B, choice (A) is correct.



SVP
Joined: 03 Jan 2005
Posts: 2233

[Edit] I'm editing this post out because I believe the tone of this post is entirely not appropriate. My apologies to all.
_________________
Keep on asking, and it will be given you;
keep on seeking, and you will find;
keep on knocking, and it will be opened to you.
Last edited by HongHu on 13 Nov 2005, 20:20, edited 1 time in total.



Current Student
Joined: 29 Jan 2005
Posts: 5218

1
This post was BOOKMARKED
HongHu wrote: This is NOT a very difficult rate problem. And DON'T do back solving unless you are absolutely clueless. Backsolving needs time. If you can express what is given in the question using algebra expressions, and if you can solve an algebra equation (both are needed if you are going to a bschool). then you would have no problem solving this question.
(10+t)A=tB=660 B=1.1A =>10A+tA=tA+0.1tA 10A=0.1tA t=100 (10+100)A=660 A=6
How simple is that?
Kaplan claims that this is a difficult rate problem, and therefore Kaplan does not offer an algebraic formula/solution to this particular problem, advocating the "backsolving" approach instead; which is exactly why I was confused and posted it in this math forum.
BTW: thanks for your condescending words of encouragement Honghu.



Director
Joined: 21 Aug 2005
Posts: 789

This was extremly difficult before 
1. The EDIT
2. "B is not the OA"
Ok after 
1. The EDIT



SVP
Joined: 03 Jan 2005
Posts: 2233

Yes exactly. Don't believe in every words Kaplan says. In fact don't believe in every words anybody says. Trust your own informed judgement is much better.
_________________
Keep on asking, and it will be given you;
keep on seeking, and you will find;
keep on knocking, and it will be opened to you.



Director
Joined: 14 Oct 2003
Posts: 583
Location: On Vacation at My Crawford, Texas Ranch

I'm not trying to sound condescending but this work rate problem is as straight forward as they come. Don't try to backsolve every problem  I don't think that's a fundamentally sound approach  you can't backsolve most of the time unless you can visualize the algebraic setup. Use the RTW (Rate, Time, Work) chart to help you visualize the relationships.
Attachments
Work problemo.JPG [ 19.2 KiB  Viewed 2671 times ]
_________________
"Wow! Brazil is big." â€”George W. Bush, after being shown a map of Brazil by Brazilian president Luiz Inacio Lula da Silva, Brasilia, Brazil, Nov. 6, 2005
http://www.nytimes.com/2005/11/21/international/asia/21prexy.html
Last edited by Titleist on 03 Nov 2005, 22:44, edited 1 time in total.



SVP
Joined: 03 Jan 2005
Posts: 2233

GMATT73 wrote: BTW: thanks for your condescending words of encouragement Honghu.
Hmmm. Oops, I didn't meant to be condescending at all. I mean some kind of bashing of the authorities on the field should be allowed shouldn't it? I apologize if I sounded that way to you. Sorry. I will try to remind myself about this next time.
_________________
Keep on asking, and it will be given you;
keep on seeking, and you will find;
keep on knocking, and it will be opened to you.



Director
Joined: 14 Oct 2003
Posts: 583
Location: On Vacation at My Crawford, Texas Ranch

BTW: thanks for your condescending words of encouragement Honghu.[/quote]
I think she was refering to Kaplan's opinion of this particular question as "a difficult rate problem." I also beg to differ with Kaplan's opinion of this problem's level of difficulty. But there was no implication about your ability whatsoever. We're all here to help one another because we all have our strengths and weaknesses  except if you're Duttsit and you appear to have no glaring weaknesses.
_________________
"Wow! Brazil is big." â€”George W. Bush, after being shown a map of Brazil by Brazilian president Luiz Inacio Lula da Silva, Brasilia, Brazil, Nov. 6, 2005
http://www.nytimes.com/2005/11/21/international/asia/21prexy.html



Senior Manager
Joined: 07 Jul 2005
Posts: 402

Two equation and Two unkowns
(a) TimeA = 10 + TimeB
(b) RateA = (1.1)RateB
Combine (a) and (b)
660/TimeB = (1.1)* 660/(10+TimeB)
TimeB = 100 hours
Therefore,
RateA = 660/110 = 6



SVP
Joined: 24 Sep 2005
Posts: 1885

HongHu wrote: This is NOT a very difficult rate problem. And DON'T do back solving unless you are absolutely clueless. Backsolving needs time. If you can express what is given in the question using algebra expressions, and if you can solve an algebra equation (both are needed if you are going to a bschool). then you would have no problem solving this question.
(10+t)A=tB=660 B=1.1A =>10A+tA=tA+0.1tA 10A=0.1tA t=100 (10+100)A=660 A=6
How simple is that?
Sis HongHu ...I know you're trying to analyze things but I think make a personal judgement on others' abilities is meaningless. We're all here to improve ourselves out of our weekness, we need encouragement from others rather than leadtonowhere judgements,right?! I'm a junior to you ...I'm not trying to be arrogant to a senior ... Just that I do hope you understand my point of view ....



SVP
Joined: 03 Jan 2005
Posts: 2233

laxieqv wrote: HongHu wrote: This is NOT a very difficult rate problem. And DON'T do back solving unless you are absolutely clueless. Backsolving needs time. If you can express what is given in the question using algebra expressions, and if you can solve an algebra equation (both are needed if you are going to a bschool). then you would have no problem solving this question.
(10+t)A=tB=660 B=1.1A =>10A+tA=tA+0.1tA 10A=0.1tA t=100 (10+100)A=660 A=6
How simple is that? Sis HongHu ...I know you're trying to analyze things but I think make a personal judgement on others' abilities is meaningless. We're all here to improve ourselves out of our weekness, we need encouragement from others rather than leadtonowhere judgements,right?! I'm a junior to you ...I'm not trying to be arrogant to a senior ... Just that I do hope you understand my point of view ....
Guys, I realize that the tone in that post of mine is not appropriate at all. Please believe me that I did not mean to be judgemental about anybody's capability at all. I was commenting about Kaplan, because I did not feel their recommendation in that case was appropriate, and it may very much mislead people. However, you are very right. The post didn't get that point accrossed. In fact it seemed to be discouraging to people. Now that I think about it, my latest posts do have the same problem. We are all learning, no matter how much we think we know. It is the helping from each other that makes us grow. Thanks for helping me with this problem. This is exactly what I needed. I promise I will try harder from now on to be more careful about my comments. We all need to learn to be respectful to our fellow posters.
(BTW sorry I didn't respond sooner. I've been a bit busy so didn't check the board for several days.)
_________________
Keep on asking, and it will be given you;
keep on seeking, and you will find;
keep on knocking, and it will be opened to you.



SVP
Joined: 16 Oct 2003
Posts: 1801

1
This post received KUDOS
Here is what I did
Work = Rate * Time
660 = 1 * (t + 10) < For A
660 = 1.1 * t < For B
Equate A and B
we get t = 100; Put this value in (A)
A takes 110 hrs to produce 660 spokets so in one hour it produces 6.



Manager
Joined: 07 May 2013
Posts: 109

Re: Machine A and machine B are each used to manufacture 660 [#permalink]
Show Tags
29 Aug 2013, 17:13
ONE EQUATION solution 660/x660/x+10 (whole divided by ) * 100=10% 660/x+10
solve for x . we get x=10 and substitute in 660/x+10 to get the answer



Math Expert
Joined: 02 Sep 2009
Posts: 39640

Re: Machine A and machine B are each used to manufacture 660 [#permalink]
Show Tags
30 Aug 2013, 04:15
Machine A and machine B are each used to manufacture 660 sprockets. It takes machine A 10 hours longer to produce 660 sprockets than machine B. Machine B produces 10% more sprockets per hour than machine A. How many sprockets per hour does machine A produce?A. 6 B. 6.6 C. 60 D. 100 E. 110 Let time needed for machine A to produce 660 sprockets be \(a\) hours, then the rate of machine A would be \(rate_A=\frac{job \ done}{time}=\frac{660}{a}\) sprockets per hour; As "it takes machine A 10 hours longer to produce 660 sprockets than machine B" then time needed for machine B to produce 660 sprockets be \(a10\) hours and the rate of machine B would be \(rate_B=\frac{job \ done}{time}=\frac{660}{a10}\) sprockets per hour; As "machine B produces 10 percent more sprockets per hour than machine A" then \(rate_A*1.1=rate_B\) > \(\frac{660}{a}*1.1=\frac{660}{a10}\) > \(a=110\) > \(rate_A=\frac{job \ done}{time}=\frac{660}{a}=6\). Answer: A. OPEN DISCUSSION OF THIS QUESTION IS HERE: machineaandmachinebareeachusedtomanufacture98696.html
_________________
New to the Math Forum? Please read this: All You Need for Quant  PLEASE READ AND FOLLOW: 12 Rules for Posting!!! Resources: GMAT Math Book  Triangles  Polygons  Coordinate Geometry  Factorials  Circles  Number Theory  Remainders; 8. Overlapping Sets  PDF of Math Book; 10. Remainders  GMAT Prep Software Analysis  SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS)  Tricky questions from previous years.
Collection of Questions: PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.
What are GMAT Club Tests? Extrahard Quant Tests with Brilliant Analytics




Re: Machine A and machine B are each used to manufacture 660
[#permalink]
30 Aug 2013, 04:15







