With DS problems, I always ask myself the following three questions:
What do I want?
What do I have?
What do I need?
The goal is not to solve but only to determine whether the statement gives you sufficient information to solve. In other words: Is the statement giving me what I need?
In this case:
What do I want? What is the question asking for?
The question is asking for the relationship -- in other words, the ratio -- between the reduced price of stock Y and the original price of stock X.
Let's say x = the original price of stock X and y = the original price of stock Y.
Stock Y is being reduced by .1y, so the reduced price is y - .1y = .9y.
So (Reduced Y)/(Original X) = (.9y)/x. This is what I want.
What do I have? Before I look at the two statements, what information have I been given?
Stock X is being increased by .1x, so increased X = x + .1x = 1.1x.
Stock Y is being decreased by .1y, so reduced Y = .9y.
What do I need? What's the missing information that I need in order to answer the question?
Since (.9y)/x = .9 * (y/x), what I need is the value of y/x.
Statement 1:
Increased X = Original Y.
1.1x = y
So y/x = 1.1. SUFFICIENT.
Statement 2:
Increase in stock X = .1x.
Decrease in stock Y = .1y.
Statement 2 says:
.1x = (10/11)(.1y)
So dividing each side by .1y we get:
(.1x)/(.1y) = 10/11
So x/y = 10/11, y/x = 11/10 = 1.1. SUFFICIENT.
The correct answer is D.
Last edited by
GMATGuruNY on Tue Jun 22, 2010 11:50 am, edited 2 times in total.
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