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Initially
B:P:W=2:50:100
That is B:P=2:50 and B:W=2:100
After altering the solution
B:P is halved i.e B:P now is 1:50
B:W is doubled i.e B:W now is 4:100
So in the new solution B:P:W=4:200:100
That makes P:W=2:1
So water = 50 cc
A is my choice
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Oh sorry...
Was posting from the iPad so the question was not available when I was typing the solution..
My bad
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The Book does not show any answers. Hence I need to figure out if I have done them correctly or not. Please help me if you can. Would greatly appropriate it. Thanks.

The ratio, by volume, of baking soda to peroxide to water in a certain solution is 2:50:100. The solution will be altered so that the ratio of baking soda to water is halved while the ratio of baking soda to peroxide is doubled. How many cubic centimeters of water will this solution contain if the altered solution will contain 100 cubic centimeters of peroxide?

A. 50
B. 200
C. 400
D. 625
E. 800

Given: \(\frac{B}{{\frac{P}{W}}}=\frac{2}{{\frac{50}{100}}}\);

The ratio of baking soda to water is halved --> \(\frac{B}{W}=\frac{1}{2}*\frac{2}{100}=\frac{1}{100}=\frac{4}{400}\);

The ratio of baking soda to peroxide is doubled --> \(\frac{B}{P}=2*\frac{2}{50}=\frac{4}{50}\);

New ratio: \(\frac{B}{{\frac{P}{W}}}=\frac{4}{{\frac{50}{400}}}\) --> \(\frac{P}{W}=\frac{50}{400}\) --> if \(P=2*50=100\) then \(W=2*400=800\).

Answer: E.

Dear Bunuel,
could u pls explain why this "2*50" to P and "2*400" is taken?
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kashishh
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The Book does not show any answers. Hence I need to figure out if I have done them correctly or not. Please help me if you can. Would greatly appropriate it. Thanks.

The ratio, by volume, of baking soda to peroxide to water in a certain solution is 2:50:100. The solution will be altered so that the ratio of baking soda to water is halved while the ratio of baking soda to peroxide is doubled. How many cubic centimeters of water will this solution contain if the altered solution will contain 100 cubic centimeters of peroxide?

A. 50
B. 200
C. 400
D. 625
E. 800

Given: \(\frac{B}{{\frac{P}{W}}}=\frac{2}{{\frac{50}{100}}}\);

The ratio of baking soda to water is halved --> \(\frac{B}{W}=\frac{1}{2}*\frac{2}{100}=\frac{1}{100}=\frac{4}{400}\);

The ratio of baking soda to peroxide is doubled --> \(\frac{B}{P}=2*\frac{2}{50}=\frac{4}{50}\);

New ratio: \(\frac{B}{{\frac{P}{W}}}=\frac{4}{{\frac{50}{400}}}\) --> \(\frac{P}{W}=\frac{50}{400}\) --> if \(P=2*50=100\) then \(W=2*400=800\).

Answer: E.

Dear Bunuel,
could u pls explain why this "2*50" to P and "2*400" is taken?

We have that \(\frac{P}{W}=\frac{50}{400}\) and \(P=100=2*50\). Now, if \(P=100\) then in order \(\frac{P}{W}=\frac{50}{400}\) to hold true W must be 800=2*400.

Or simply: \(\frac{P}{W}=\frac{50}{400}=\frac{100}{800}\).
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Bumping for review and further discussion*. Get a kudos point for an alternative solution!

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1. Let the volume of the original solution be v. The ratio of baking soda to peroxide to water is 2:50:100
2. v= 2x+50x+100x
3. The ratio of baking soda to peroxide is doubled and the ratio of baking soda to water is halved.
4 The volume is the same. v= 2y+25y+200y
5. We see if the peroxide is 25 cu.cm, water is 200 cu.cm. If peroxide is 100 cu.cm , water contained is 800 cu.cm
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Ratio to BS/Perox/water = 2/50/100 ; If you halved the ratio of Perox / water =(50/100) *(1/2)= 25/100
At the same time the ratio of BS / Perox is doubled =2/25= 2*(2/50)
Hence the final answer = 2/ 25/100
When perox = 100 = 25*4
Therefore the water = 400

Thanks

:-D
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I took initial ratio given in statement:
S:P:W --> 2:50:100

I altered it based on the info of the statement:
halved S : W --> 2:200
doubled S:P --> 4:50

new ratio is:
S:W:P--> 4:400:50

Extra info: 100l of P (from statement)
Thus: 50x=100 --> x=2
Use x=2 to find liters of water in the solution. 400*2=800l of water

:)

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Hello from the GMAT Club BumpBot!

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