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If Tom invest $x April at a constant monthly interest rate o

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by Max@Math Revolution » Sun Jun 26, 2016 5:29 pm
If Tom invest $x April at a constant monthly interest rate of y percent, what is the percent increase from April to October?
1) x=10,000
2) y=2

*An answer will be posted in 2 days.
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Source: — Data Sufficiency |
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by 800_or_bust » Mon Jun 27, 2016 8:00 am
Max@Math Revolution wrote:If Tom invest $x April at a constant monthly interest rate of y percent, what is the percent increase from April to October?
1) x=10,000
2) y=2

*An answer will be posted in 2 days.
(1) Not sufficient. We need to know the value of y to determine the percent increase. The principal amount does not matter.

(2) Sufficient. This provides a value of y, and hence we could determine the overall percent change. The principal does not matter, as that would impact only the actual dollar amount of the accrued interest and not the percentage.

Answer: B
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by Max@Math Revolution » Tue Jun 28, 2016 5:32 pm
If we modify the original condition and the question, we get x--> x(1+y%)^6. Hence, for the percent increase, we only have to know the value of y. Thus, the correct answer is B.


- Forget conventional ways of solving math questions. In DS, Variable approach is the easiest and quickest way to find the answer without actually solving the problem. Remember equal number of variables and independent equations ensures a solution.
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