Princeton..MegaSaver & InvestPro..pg no.178

This topic has expert replies
User avatar
Legendary Member
Posts: 752
Joined: Sun Sep 12, 2010 2:47 am
Thanked: 20 times
Followed by:10 members
GMAT Score:700
A certain bank offers two different savings accounts : MegaSaver & InvestPro.Does MegaSaver offer a greater return over a 5-year period than InvestPro?

1) MegaSaver has an interest rate of 3% paid quarterly.InvestPro has an interest rate of 4% paid semi-anually.
2) The MegaSaver account will first pay a return at least 100% greater than the InvestPro account after 17.5 years.

Source :Princeton
OA : later
Source: — Data Sufficiency |

User avatar
GMAT Instructor
Posts: 905
Joined: Sun Sep 12, 2010 1:38 am
Thanked: 378 times
Followed by:123 members
GMAT Score:760

by Geva@EconomistGMAT » Wed Dec 29, 2010 11:16 pm
I don't think the question is phrased properly, or clearly, so I'm not 100% sure of this. I'm making the assumption that we're asked to compare returns based on the same initial Principal. i.e.. if we invest the same amount (e.g. $100) in each of the programs, which account will have a greater balance after 5 years? If we can also play around with the initial Principal, then the answer is E: you can always claim that you invest $1 in one program and $10000 in the other, or vice versa, and receive a greater return on the $10000 one, regardless of interest rates.

Under this assumption, it comes down solely to interest rate: whichever of the programs offers a greater annual interest rate will have a greater return. If one program gives 10% and the other only 8%, then the first program will offer better returns consistently after 1 year, 5 years or 10 years. So the issue of the question is "which of these programs have a greater annual interest rate?"

Stat. (1): sufficient, and there is absolutely no need to calculate the returns. This statement basically gives you the interest rates of each program: using the data, you should be able to plug in $100 in each and find the return after 5 years, at which point you will have enough data to answer the question one way or the other.
Caveat: the only ambiguity here is if it is possible for one account to be simple interest and the other compound, or vice versa.

Stat (2): If the mega saver pay a greater return at any point (be it 17.5 or any other years after), then it must have a greater interest rate - which means that it must also pay a greater interest rate after 5 years. The answer is yes, and sufficient.

So the answer is D, unless whoever wrote the question left it ambiguous intentionally in order to allow you to play with two parameters: initial Principal, and simple Vs. Compound interest. Not a very good question, IMHO.
Geva
Senior Instructor
Master GMAT
1-888-780-GMAT
https://www.mastergmat.com