Events & Promotions
|
|
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
Track
Your Progress
Practice
Pays
Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.
Apr 2212:30 AM EDT
-01:30 AM EDT
At one point, she believed GMAT wasn’t for her. After scoring 595, self-doubt crept in and she questioned her potential. But instead of quitting, she made the right strategic changes. The result? A remarkable comeback to 695. Check out how Saakshi did it.
Apr 1612:00 PM EDT
-11:59 PM EDT
You’re first to know: Save $200 on GMAT prep starting tomorrow, 4/13. Get 6 official practice tests and study with real questions. Be ready to save!
Apr 2301:30 AM EDT
-02:30 AM EDT
Struggling with GMAT Verbal as a non-native speaker? Harsh improved his score from 595 to 695 in just 45 days—and scored a 99 %ile in Verbal (V88)! Learn how smart strategy, clarity, and guided prep helped him gain 100 points.
Apr 2308:00 PM PDT
-09:00 PM PDT
Video explanations + diagnosis of 10 weakest areas + 150+ short videos + study plan!
Apr 2610:00 AM EDT
-11:00 AM EDT
The Target Test Prep course represents a quantum leap forward in GMAT preparation, a radical reinterpretation of the way that students should study. Try before you buy with a 5-day, full-access trial of the course for FREE!
Apr 2711:00 AM EDT
-12:00 PM EDT
Prefer video-based learning? The Target Test Prep OnDemand course is a one-of-a-kind video masterclass featuring 400 hours of lecture-style teaching by Scott Woodbury-Stewart, founder of Target Test Prep and one of the most accomplished GMAT instructors
Apr 2808:00 AM PDT
-11:00 AM PDT
Whether you are just beginning your MBA journey or fine-tuning your path to a 700+ score, GMAT Day is designed to give you a competitive edge.
09 Sep 2015, 02:28
Kudos
Bookmarks
E
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
75%
(hard)
Question Stats:
65% (03:00) correct
35%
(03:18)
wrong
based on 1069
sessions
History
Date
Time
Result
Not Attempted Yet
Machine A takes 2 more hours than machine B to make 20 widgets. If working together, the machines can make 25 widgets in 3 hours, how long will it take machine A to make 40 widgets?
(A) 5
(B) 6
(C) 8
(D) 10
(E) 12
(A) 5
(B) 6
(C) 8
(D) 10
(E) 12
13 Sep 2015, 07:59
Kudos
Bookmarks
Bunuel
VERITAS PREP OFFICIAL SOLUTION:
We need to find the time taken by machine A to make 40 widgets. It will be best to take the time taken by machine A to make 40 widgets as the variable x. Then, when we get the value of x, we will not need to perform any other calculations on it and hence the scope of making an error will reduce. Also, value of x will be one of the options and hence plugging in to check will be easy.
Machine A takes x hrs to make 40 widgets.
Rate of work done by machine A = Work done/Time taken = \(\frac{40}{x}\)
Machine B take 2 hrs less than machine A to make 20 widgets hence it will take 4 hrs less than machine B to make 40 widgets. Think of it this way: Break down the 40 widgets job into two 20 widget jobs. For each job, machine B will take 2 hrs less than machine A so it will take 4 hrs less than machine A for both the jobs together.
Time taken by machine B to make 40 widgets = x – 4
Rate of work done by machine B = Work done/Time taken = \(\frac{40}{(x - 4)}\).
We know the combined rate of the machines is 25/3
So here is the equation:
\(\frac{40}{x} + \frac{40}{(x - 4)} = \frac{25}{3}\)
The steps till here are not complicated. Getting the value of x poses a bit of a problem.
Notice here that that the right hand side is not an integer. This will make the question a little harder for us, right? Wrong! Everything has its pros and cons. The 3 of the denominator gives us ideas for the values of x (as do the options). To get a 3 in the denominator, we need a 3 in the denominator on the left hand side too.
x cannot be 3 but it can be 6. If x = 6, \(\frac{40}{(6 - 4)} = 20\) i.e. the sum will certainly not be 20 or more since we have \(\frac{25}{3} = 8.33\) on the right hand side.
The only other option that makes sense is x = 12 since it has 3 in it.
\(\frac{40}{12} + \frac{40}{(12 - 4)} = \frac{10}{3} + 5 = \frac{25}{3}\)
Answer (E)
If we did not have the options, we might have tried x = 9 too before landing on x = 12. Nevertheless, these calculations are not time consuming at all since you can get rid of the incorrect numbers orally. Making a quadratic and solving it is certainly much more time consuming.
Another method could be to bring 3 to the left hand side to get the following equation:
\(\frac{120}{x} + \frac{120}{(x - 4)} = 25\)
This step doesn’t change anything but it helps if you face a mental block while working with fractions. Try to practice such questions using these techniques – they will save you a lot of time.
21 Nov 2016, 23:32
Kudos
Bookmarks
Bunuel
Here is how you can do it without any variables:
Together they make 25 widgets in 3 hrs
So to make 40 widgets, together they take 3*(40/25) = 4.8 hrs
So each individually will certainly take more than 4.8 hrs to make 40 widgets.
Machine A takes 2 extra hrs to make 20 widgets so it will take 4 extra hrs to make 40 widgets. So machine A will certainly take more than 8.8 hrs to make 40 widgets. So we need to pick out of (D) and (E) only.
Try (D) - If A takes 10 hrs, B takes 6 hrs and together they 1/(1/10 + 1/6) = 60/16 (less than 4 hrs)
Hence answer must be (E).
