This question is quite tricky and requires us to create equations for what has been expressed in the question.
The first part of the question states that "a mixture of orange and carrot juices consists of x liters of orange juice and y liters of carrot juice. What percent of the mixture, by volume, is orange juice?"
We understand that there is this unit of a "mixture" which consists of x litres of orange juice and y liters of carrot juice. Let's just call it Drink or D for short. D can be expressed very simply as
\(D=x+y\)
To us it does not really matter how many liters the drink is or how many liters each component is but rather what
percent of the mixture is orange juice. So we are looking for the ratio of orange juice to the drink as a whole.
Let the %O be written simply as P
We can therefore express the percentage of orange juice (P) with respect to the drink as
\(\frac{x}{x+y}=P\)
The first statement that is given says that
(1) "If 2 liters of carrot juice were replaced with 2 liters of orange juice, the percentage of orange juice by volume in the mixture would double."
We can express this as follows
\(\frac{x+2}{x+y}=2P\)
it is x+2 because since we are replacing 2 liters of carrot juice with 2 liters of orange juice, then we are adding 2 liters to the overall amount of orange juice. Moreover, the total amount of liquid does not change because we are replacing 2 liters with 2 liters. The percentage of orange juice will change however the total volume of the liquid will remaind the say. It also states that the percentage of orange juice would double and therefore it is 2P.
Now let us combine these two equations
\(\frac{x}{x+y}=P\)
\(\frac{x+2}{x+y}=2P\)
We can plug in the value for P
\(\frac{x+2}{x+y}=\frac{2x}{x+y}\)
The (x+y)'s cancel out and we get \(2x=x+2\) or simply \(x=2\)
Therefore we know that there are 2 liters of orange juice that we can calculate with the information provided in statement (1). However, the question is asking for the percentage of orange juice in the mixture. We cannot find this out with the information provided because we have two unknowns: the volume of carrot juice and the percentage of orange juice.
Now the second statement is quite interesting
(2) "If half of the carrot juice by volume were replaced with an equal amount of orange juice, the percentage of orange juice by volume in the mixture would double."
On the surface it looks like it will yield a similar result to the first statement. However, let's go ahead and write out the equations.
These two equations we can deduce from the question prompt
\(D=x+y\) where D is the drink
\(\frac{x}{x+y}=P\) where P is the percentage of orange juice
and this equation we get from statement (2)
Since the volume of carrot juice is expressed as y, replacing "half of the carrot juice by volume" with orange juice can be expressed as \(x+\frac{y}{2}\). It also states that in doing so, the percentage of orange juice by volume in the mixture would double. So here is the final equation.
\(\frac{x+0.5y}{x+y}=2P\)
Now, as we did with the first statement, we can combine the two equations together.
\(\frac{x+0.5y}{x+y}=2P\)
\(\frac{x}{x+y}=P\)
I can rewrite the top equation as
\(\frac{2x+y}{2(x+y)}=2P\)
\(\frac{x}{x+y}=P\)
Now I can simplify the equations
\(2x+y=4P(x+y)\)
\(X=P(x+y)\)
*Note: it is quite difficult to write out the mathematical notations on computer and therefore extra steps might be added*
We can multiply the bottom equation by 4
\(2x+y=4P(x+y)\)
\(4x=4P(x+y)\)
Now we can equate these to get
\(2x+y=4x\)
\(2x=y\)
Now this is interesting because we have a ratio of x to y, or orange juice to carrot juice. We know that there is twice the amount of carrot juice to orange juice.
So now we know that \(D=x+y\) can be written as \(D=3x\) and if we go back to our earlier equation \(\frac{x}{x+y}=P\). We can now write this as \(\frac{x}{3x}=P\) or just \(\frac{1}{3}=P\)
therefore our percentage of orange juice is equal to 33%. So we
CAN calculate the percent of orange juice in the mixture with Statement (2) ALONE but not with Statement (1) alone
Therefore the answer is B
Bunuel
A mixture of orange and carrot juices consists of x liters of orange juice and y liters of carrot juice. What percent of the mixture, by volume, is orange juice?
(1) If 2 liters of carrot juice were replaced with 2 liters of orange juice, the percentage of orange juice by volume in the mixture would double.
(2) If half of the carrot juice by volume were replaced with an equal amount of orange juice, the percentage of orange juice by volume in the mixture would double.
A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient to answer the question asked.
B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient to answer the question asked.
C. BOTH statements (1) and (2) TOGETHER are sufficient to answer the question asked, but NEITHER statement ALONE is sufficient to answer the question asked.
D. EACH statement ALONE is sufficient to answer the question asked.
E. Statements (1) and (2) TOGETHER are NOT sufficient to answer the question asked, and additional data specific to the problem are needed.