Solution

To find:

• The number of basic units of currency X, which are equivalent to 250 basic units of currency Y

Analysing Statement 1

• As per the information given in statement 1, 100 basic units of currency X are equivalent to 625 basic units of currency Y

o Therefore, 250 basic units of currency Y = \(\frac{100}{625} * 250\)

Hence, statement 1 is sufficient to answer

Analysing Statement 2

• As per the information given in statement 1, 2000 basic units of currency X are equivalent to 12500 basic units of currency Y

o Therefore, 250 basic units of currency Y = \(\frac{2000}{12500} * 250\)

Hence, statement 2 is sufficient to answer

Hence, the correct answer is option D.

Answer: D
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Answer should be E right ? We can't find the relation if its a straight line or parabola or anything else? Even with both the statements included. Please help.

It is interesting to notice that both answer choices basically say the same, because statement two is a multiple of statement one (factor 20).

I am still choosing D, because a currency conversion is always a straight line. e.g. 1 EUR = 1,15 USD. Therefore, 2 EUR = 2,30 USD. The same reasoning applies to this question.

Hello

I think in this case relation should be fairly simple and straight (line). If 'a' units of currency X are equal to 'b' units of currency Y, then
1 unit of currency X = b/a units of currency Y and
1 unit of currency Y = a/b units of currency X

Can anyone help me understand why my-setup is wrong?

Notice statement 1 and 2 are the same.
Correct answer is choice D. I chose answer choice E because my algebra came down to 3V2E. 3 variables but only 2 equations, therefor it is not sufficient, or I thought.


My setup was (#)(X) units = (250)(Y)? Trying to solve for #.

1.) 100X=625Y "100 units of currency X are equivalent to 625 unit of Y" (doesn't "of" mean multiply?)
2.) 2000X=12500Y

Hello theAlchemist89,

In trying to solve for #, you could have also taken the ratio approach. That would have helped you understand that this is just not another question on equations. Do not take the variable approach all the time, GMAT Math is about using smart numbers.

If you dig a little deeper, you will see that the individual statements are sufficient because they give us the ratio of X and Y. Let's see.

Statement I alone says that 100 basic units of X are equivalent to 625 basic units of Y. This means 100 * X = 625 * Y, which can be reorganised and written as X/Y = 4/25. This means that every 4 basic units of X is equivalent to 25 basic units of Y. This can help us find out the X equivalent of 250 units of Y.

Statement II alone says that 2000 basic units of X are equivalent to 12500 basic units of Y. This means 2000 * X = 12500 * Y, which can be reorganised and written as X/Y = 4/25. This again means that every 4 basic units of X is equivalent to 25 basic units of Y. This can help us find out the X equivalent of 250 units of Y.

That's how the individual statements are sufficient when taken alone. That's why the correct answer is D.

Also, 'Of' can mean multiplication but it's usually used with fractions, decimals, percentages etc., to signify 'so many times of'.

Hope that helps!
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Thank you so much for the elaborate explanation and mentioning to not always approach it as algebra, which I usually default to. ( I know this sentence is not in parallel form =)

Please double-check your explanation. Did you mean to write 100 * X = 625 * Y? That will not give you X/Y=4/25. Similarly, for statement 2, it can't be 200 * X = 12500 * Y.

and Dedicated Data Sufficiency (DS) Course

Answer: Option D

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Solution:


Question Stem Analysis:

We need to determine the number of basic units of currency X that are equivalent to 250 basic units of currency Y. We can let this number be x.

Statement One Alone:

With the information in statement one, we can create the proportion:

x/250 = 100/625

We see that we can determine a value of x, so statement one alone is sufficient.

Statement Two Alone:

With the information in statement two, we can create the proportion:

x/250 = 2,000/12,500

We see that we can determine a value of x, so statement two alone is sufficient.

Answer: D
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If any option gave a reduced fraction, it would have been wrong since the question asks for number of units. And units have to be a non -ve integer. Am I right?