more gmat prep

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more gmat prep

by awilhelm » Mon Jan 26, 2009 10:08 pm
If 1,000 is deposited in a certain bank account and remains in the account and any accumulated interest, I, earned by the deposit in the first n years is given by the formula I = 1,000((1 + r/100)^n - 1), where r percent is the annual interest rate paid by the band, is the annual interest rate paid by the bank greater than 8 percent?

1) The deposit earns a total of $210 in interest in the first 2 years
2) (1 + r/100)^2 > 1.15
Source: — Data Sufficiency |

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by DanaJ » Tue Jan 27, 2009 12:18 am
1. 1,000((1 + r/100)^2 - 1) = 210. This means that (1 + r/100)^2 - 1 = 0.21 or that (1 + r/100)^2 = 1.21. Since 1.21 = 1.1^2, we can safely say that 1 + r/100 = 1.1 or that r/100 = 0.1. This means r = 10, which is greater than 8. So 1 is sufficient.

2. Let's calculate (1 + 8/100)^2 = (1.08)^2 = 1.166. But since (1 + r/100)^2 > 1.15, we cannot say if it is greater than 1.166 as well. So 2 is insufficient.

I'd go with A.

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by awilhelm » Tue Jan 27, 2009 8:23 am
Thanks, Dana.