Find all School-related info fast with the new School-Specific MBA Forum

It is currently 23 Aug 2014, 02:11

Close

GMAT Club Daily Prep

Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track
Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

How to solve these types of question efficiently?

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:
Manager
Manager
avatar
Joined: 10 Aug 2009
Posts: 123
Followers: 3

Kudos [?]: 12 [0], given: 13

How to solve these types of question efficiently? [#permalink] New post 22 Feb 2010, 07:36
Hi,

I've noticed that the following type of question appears very often:

"Someone bought x amount of product 1 for some price, and y amount of product 2 for some other price. The total amount of the purchase was Z. How much of each did he buy?"

For the easiest ones you can just run through all the multiples of the prices and find the answer, but this is extremely inefficient. You can find the value of y in terms of x and you may get lucky (i.e. x has to be divisible by 5). Is there a fast way to solve these problems?
1 KUDOS received
Manhattan GMAT Instructor
User avatar
Joined: 27 Aug 2009
Posts: 153
Location: St. Louis, MO
Schools: Cornell (Bach. of Sci.), UCLA Anderson (MBA)
Followers: 125

Kudos [?]: 198 [1] , given: 6

Re: How to solve these types of question efficiently? [#permalink] New post 22 Feb 2010, 13:52
1
This post received
KUDOS
In a DS context, these problems are sometimes about spotting a certain combination of variables.

For example
At a certain store, all t-shirts have the same price and all hats have the same price. What is the total price of 2 t-shirts and 5 hats?
Translation: What is (2T + 5H)?

(1) The total price of 4 t-shirts and 10 hats is $50.
Translation:
4T + 10H = $50
2(2T + 5H) = $50
Therefore, (2T + 5H) = $50/2 = $25

Plugging in test numbers would potentially cost a lot of time unnecessarily; we don't care about T and H individually, so it doesn't pay to plug in for them individually.
Take-away: Translate to algebra, and if the question concerns a combination of variables, look for that combo in the statements.

In other DS questions, these scenarios can be about an implied integer constraint.

For example
The post office sells only 3 cent stamps and 16 cent stamps. If a total of 25 stamps were sold on Wednesday, how many 3 cent stamps were sold on Wednesday?

(1) The total price of the stamps sold on Wednesday was more than $2.72 and less than $2.95.
Translation:
3x + 16y = total, which is in the range 272 to 295.
x + y = 25

For such a small range for total price (23 cents is not much more than a single 16 cent stamp!), it is worth it to plug in some possible x and y pairs to see how many give a total in the range (it's gonna be one or two pairs that work).

To keep the time manageable, just be organized about it.

15*(16 cents) = 240 and 10*(3 cents) = 30. Total = 270...too low.
16*(16 cents) = 256 and 9*(3 cents) = 27. Total = 283...OK.
17*(16 cents) = 272 and 8*(3 cents) = 24. Total = 296...too high.

The number of 3 cent stamps must be 9, SUFFICIENT.
Take-away: Don't be lazy about plugging on DS; you might see the trick with just a little work.

If you see this on PS, some plugging is probably necessary too.

For example
At a certain store, all t-shirts have the same integer price and all hats have the same integer price. Which of the following could be the total price of 2 t-shirts and 6 hats?

Tips:
(1) Factor as much as you can. What could be 2T + 6H? ---> What could be 2(T+3H)? The answer will be even.
(2) If you must plug, do so in a chart. Be organized. Look for patterns. Cross off answers as you go.
Take-away: Be neat, and trust the process. The problems are designed to be done in 2 minutes, so how bad can plugging be?
_________________


Emily Sledge | Manhattan GMAT Instructor | St. Louis

Manhattan GMAT Discount | Manhattan GMAT Course Reviews | Manhattan GMAT Reviews

Manager
Manager
avatar
Joined: 10 Aug 2009
Posts: 123
Followers: 3

Kudos [?]: 12 [0], given: 13

Re: How to solve these types of question efficiently? [#permalink] New post 23 Feb 2010, 04:36
Thanks esledge. I guess plugging is inevitable, I'll do my best to be organised about it. The thing is that I get nervous when I have to do a lot of plugging (I start to think that maybe there is a shortcut that I'm missing, which I why I asked this question actually).
Re: How to solve these types of question efficiently?   [#permalink] 23 Feb 2010, 04:36
    Similar topics Author Replies Last post
Similar
Topics:
11 Experts publish their posts in the topic How to Efficiently Solve RC a Video Lecture by e-GMAT bb 15 12 Nov 2012, 09:46
2 Experts publish their posts in the topic How many different 7 digit members are their sum of whose zareentaj 9 07 Aug 2010, 05:10
A math question -how to solve MBA2ran 3 24 Oct 2006, 10:29
How to solve Work questions andy_gr8 3 01 Dec 2005, 22:04
Display posts from previous: Sort by

How to solve these types of question efficiently?

  Question banks Downloads My Bookmarks Reviews Important topics  


cron

GMAT Club MBA Forum Home| About| Privacy Policy| Terms and Conditions| GMAT Club Rules| Contact| Sitemap

Powered by phpBB © phpBB Group and phpBB SEO

Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.