miweekend wrote:

perseverant wrote:

An investment of d dollars at k percent simple annual interes yields $600 interest over a 2 year period. In terms of d, what dollar amount invested at the same rate would yield $2400 of interest over a 3 year period?

a)(2d)/3

b)(3d)/4

c)(4d)/3

d)(3d)/2

e)(8d)/3

This is a question I got wrong in my GMATPrep test. Could someone help me get to the right answer?

Thanks!

I got E but I'm not sure if my calculation is correct...quite weird. can anyone pls enlighten? thanks!

My way:

Case 1: d * k/100 * 2 = 600 (for 2 years period)

Case 2: d * k/100 * 3 = 2400 (for 3 years period)

So 2kd / 100 = 600 versus 3kd / 100 = 2400

=> 2kd = 60000 : 3kd = 240000

=> 2kd/60000 = 3kd/240000

=> 180000kd = 480000kd

=>3/8 kd

=> k = (8/3)d

I see that you got the answer right. I'd rather do it this way:

\(d*\frac{k}{100}*2=600\)

\(k=\frac{30000}{d}\)---------------------1

We got our rate in terms of d; let the new principal be x; now, we take the other case:

\(x*\frac{k}{100}*3=2400\)

\(x=\frac{80000}{k}\)

Write k in terms of d;

\(x=\frac{80000d}{30000}=\frac{8d}{3}\)

Ans: "E"

_________________

~fluke

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