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.

It appears that you are browsing the GMAT Club forum unregistered!

Signing up is free, quick, and confidential.
Join other 500,000 members and get the full benefits of GMAT Club

Registration gives you:

Tests

Take 11 tests and quizzes from GMAT Club and leading GMAT prep companies such as Manhattan GMAT,
Knewton, and others. All are free for GMAT Club members.

Applicant Stats

View detailed applicant stats such as GPA, GMAT score, work experience, location, application
status, and more

Books/Downloads

Download thousands of study notes,
question collections, GMAT Club’s
Grammar and Math books.
All are free!

Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:

Bag A contains red, white and blue marbles such that the red to white marble ratio is 1:3 and the white to blue marble ratio is 2:3. Bag B contains red and white marbles in the ratio of 1:4. Together, the two bags contain 30 white marbles. How many red marbles could be in bag A? 1 3 4 6 8

Bag A: R/w = 1/3 and w/b=2/3 Bag B: R/w = 1/4

Number of White marbles in A and B is 30 . i.e A+B =30

so in Bag B Number of white marbles will be 30/5 * 4 = 24

since A+B = 30 => B= 24 then in Bag A number of white marbles will be 6

Now R/w = 1/3 => R/6 = 1/3 => R=2

But there is NO 2. what i'm doing wrong. please explain.

Bag A contains red, white and blue marbles such that the red to white marble ratio is 1:3 and the white to blue marble ratio is 2:3. Bag B contains red and white marbles in the ratio of 1:4. Together, the two bags contain 30 white marbles. How many red marbles could be in bag A? 1 3 4 6 8

Bag A contains red, white and blue marbles such that the red to white marble ratio is 1:3 and the white to blue marble ratio is 2:3. Bag B contains red and white marbles in the ratio of 1:4. Together, the two bags contain 30 white marbles. How many red marbles could be in bag A? 1 3 4 6 8

So, both 2 and 6 are possible numbers of red marbles in Bag A.

Ans: "D"

Thank you for your detail explanation. just little confusion. how did you get the red part. because i have to solve it through making equations R/w = 1/3 w/b=2/3 => R/b = 2/9 after this i don't know how to set up R:W:B I assume that you have used some short cut.
_________________

Thank you for your detail explanation. just little confusion. how did you get the red part. because i have to solve it through making equations R/w = 1/3 w/b=2/3 => R/b = 2/9 after this i don't know how to set up R:W:B I assume that you have used some short cut.

Not really;

Just take the LCM of the common term:

R:W=1:3 --------1 W:B=2:3 --------2

Here W is common; Take the LCM of 2,3=6

So, eq 1 needs to be multiplied by 2: R:W=(1:3)*2=2:6---------3

So, eq 2 needs to be multiplied by 3: W:B=(2:3)*3=6:9---------4

Now; 3 and 4 are both 6 whites; we can join them R:W:B 2:6:9
_________________

Bag A contains red, white and blue marbles such that the red to white marble ratio is 1:3 and the white to blue marble ratio is 2:3. Bag B contains red and white marbles in the ratio of 1:4. Together, the two bags contain 30 white marbles. How many [highlight]red marbles could be in bag A[/highlight]? [/[color=#40FF00]color]

a 1 b 3 c 4 d 6 e 8

Bag A: R:W = 1:3 W:B = 2:3 W is the common one here so make it equal i.e. R:W = 2:6 and W:B = 6:9 (the ratios remain the same). So R:W:B = 2:6:9 Since number of marbles has to be an integer, number of red marbles in this bag must be 2 or a multiple of 2 and number of white marbles must be 6 or a multiple of 6.

Bag B: R:W = 1:4 The number of white marbles must be 4 or a multiple of 4.

To make 30 white marbles, you could mix white marbles from Bag A and Bag B in many ways. BagA: 6 + BagB: 24 (No. of red marbles in BagA = 2) BagA: 12 + BagB: 18 - Not possible because 18 is not a multiple of 4 BagA: 18 + BagB: 12 (No. of red marbles in BagA = 6) BagA: 24 + BagB: 6 - Not possible because 6 is not a multiple of 4

No of red marbles in bag A can be both 2 and 6. Answer (D)
_________________

ratio of balls in bag A: red:white:blue -->2:6:9 (2x+6x+9x) ratio of balls in bag B: red:white --->1:4 (1y+4y)

so we can derive a equation where white balls in both bags--> 6x+4y=30 -----1 (as the total number of white balls are 30) red balls in bag A ---> 2x=?------2

solving eqn 1 --> we get x value as 1 and 3 to get a whole number as balls cannot be in fraction.

substituting the value in 2 --> we get the value as 2 and 6 for red balls in bag A. As 2 is not there in the answer , we select 6 (ie answer D)

ratio of balls in bag A: red:white:blue -->2:6:9 (2x+6x+9x) ratio of balls in bag B: red:white --->1:4 (1y+4y)

so we can derive a equation where white balls in both bags--> 6x+4y=30 -----1 (as the total number of white balls are 30) red balls in bag A ---> 2x=?------2

solving eqn 1 --> we get x value as 1 and 3 to get a whole number as balls cannot be in fraction.

substituting the value in 2 --> we get the value as 2 and 6 for red balls in bag A. As 2 is not there in the answer , we select 6 (ie answer D)

Nothing wrong with the method. Essentially, both, this one and the one above, find integral solutions of 6x + 4y = 30.
_________________

Re: MGMAT PS: Bag A contains red, white and blue marbles [#permalink]

Show Tags

21 Sep 2011, 10:00

D) 6

Let x be the # of Red balls in Bag A Therefore the ratio for R/W = 1/3 = x/3x

Let y be the # of Red balls in Bag B Therefore the ratio for R/W = 1/4 = y/4y

Now we know White (Bag A) + White (Bag B) = 30 3x + 4y = 30

So lets see what value of x solves this equation from the choices given: 1, 3, 4, 6, 8 1: y is not an integer (27/4) 3: y is not an integer (21/4) 4: y is not an integer (14/4) 6: y is an integer 8: y is not an integer