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An investment of d dollars

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mgmat
 Post subject: An investment of d dollars
 Post Posted: Thu Apr 24, 2008 11:55 am 
An investment of d dollars at k percent simple annual interest yields $600 over a 2 year period. In terms of d, what dollar amount invested at the same rate will yield $24,000 over a 3 year period?

A. (2d)/3
B. (3d)/4
C. (4d)/3
D. (3d)/2
E. (8d)/3 - Correct Answer

Maybe Vics may work but I couldn't approach this correctly. How do you do this?
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rfernandez
 Post subject:
 Post Posted: Thu Apr 24, 2008 5:29 pm 
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ManhattanGMAT Staff


Posts: 386
I suspect you may have a typo... can you double check on the amount you want to yield in the question... is it $24,000 or $2,400?
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mgmat
 Post subject: yes
 Post Posted: Sat Apr 26, 2008 1:04 pm 
rey, you are correct. it's 2,400. sorry.
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rfernandez
 Post subject:
 Post Posted: Fri May 02, 2008 3:45 pm 
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ManhattanGMAT Staff


Posts: 386
A VIC solution might look like this:

Choose d = 1000 and k = 30. I chose these numbers because $600 of simple interest over two years means $300 each year, and 30% of $1000 is $300.

So now, we need to find the target value, namely the size of the investment needed to yield $2400 in interest over three years, at the same rate k.

Interest = (Principal)(rate)(time)
2400 = P(.3)(3)
P=8000/3

Now, plugging in 1000 in for d in the five answer choices only gives one match, choice E.

Rey
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kevincan
 Post subject:
 Post Posted: Wed May 14, 2008 5:35 pm 
Think that you need to generate 4 times as much interest , so multiply d by 4= 4d
However, you are given 3/2 as much time, so multiply 4d by 2/3 =8d/3

Kevin Armstrong
Madrid, Spain
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charlottetaylor.07
 Post subject: Re: An investment of d dollars
 Post Posted: Tue Oct 05, 2010 9:05 am 
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Course Students


Posts: 2
Can someone post the algebraic way of getting this answer please? Here's what I did and I can't seem to get the right answer...

Prt= (d)(k/100)(2)= 600
k= 30,000/d

24000=P(30,000/d)(3)
P=2d/75
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Viswanathan.harsha
 Post subject: Re: An investment of d dollars
 Post Posted: Wed Oct 06, 2010 12:45 am 
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Course Students


Posts: 46
The way I see is:

600 = d1 (k/100) (2)
2400 = d2 (k/100) (3)

Hence:
300=d1 (k/100)
800=d2 (k/100)

k/100 is constant in both, so disregard, and you can see the 8/3 relationship of d in the two equations.
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tim
 Post subject: Re: An investment of d dollars
 Post Posted: Fri Oct 08, 2010 4:00 am 
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Posts: 2192
Location: Southwest Airlines, seat 21C
Looks good..

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Tim Sanders
Manhattan GMAT Instructor
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