Question from Gmat Prep- Help please! 4

[bobdylan]

An investment of d dollars at k percentsimple annual interest yield $600 interest over a 2-year period. In terms of d, what dollar amount invested at the same rate will yield $2,400 interest over a 3-year period?
a) 2d/3
b)3d/4
c)4d/3
d)3d/2
e)8d/3

[GMATGuruNY]

An investment of d dollars at k percent simple annual interest yields $600 interest over a 2-year period. In terms of d, what dollar amount investment at the same rate will yield $2,400 interest over a 3-year period?

a) 2d/3
b) 3d/4
c) 4d/3
d) 3d/2
e) 8d/3

Thanks,

We can plug in values.

Let k = 100% annual interest.
Thus, the amount of interest per year = the amount invested.

$600 interest over 2 years = $300 interest per year.
To earn $300 interest per year, the amount invested = d = 300.

$2400 interest over 3 years = $800 interest per year.
To earn $800 interest per year, the amount invested = $800. This is our target.

Now we plug d=300 into the answers to see which yields our target of 800.

Only answer choice E works:
8d/3 = 8*300/3 = 800.

The correct answer is E.

[Shalabh's Quants]

An investment of d dollars at k percentsimple annual interest yield $600 interest over a 2-year period. In terms of d, what dollar amount invested at the same rate will yield $2,400 interest over a 3-year period?
a) 2d/3
b)3d/4
c)4d/3
d)3d/2
e)8d/3

We know that SI = P.r.t/100; where P= principal, r= rate and t= time,

then, 600 = d*k*2/100

=> k = 30000/d;

Again from II condn. 2400 = P*k*3/100;

By placing the value of k, we get P = 8d/3.

[shubham_k]

from basics we are aware that intrest is p*n*r/100.(pricipal number of years and rate respectively).
thus 600 = 2*r*p/100 hence r*p/100 = 300,

Also 2400 = 3*r*p1/100 now substituting r/100 as 300/p so we get
2400 = 3*300*p1/p
thus we get p1=8p/3


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[Anurag@Gurome]

An investment of d dollars at k percentsimple annual interest yield $600 interest over a 2-year period. In terms of d, what dollar amount invested at the same rate will yield $2,400 interest over a 3-year period?
a) 2d/3
b)3d/4
c)4d/3
d)3d/2
e)8d/3

Simple interest = principal * interest rate * time, where
principal = amount invested
rate = interest rate

An investment of d dollars at k percent simple annual interest yields $600 over a 2 year period implies d * k/100 * 2 = 600
k = 30,000/d

Let us assume that the amount invested at the same rate which will yield $2,400 over a 3 year period = $x

Then, x * k/100 * 3 = 2400
x * (30000/100d) * 3 = 2400
x = [spoiler]8d/3[/spoiler]

The correct answer is E.