Saturday, October 31, 2009

Algebra problem, figuring rate of return.?

Suppose that you invested $16,000 in a high-risk growth fund that after 2 years was worth $25,000. Your broker used the following equation to find the average annual rate of return, (r)



16,000(1 + r)2 = 25,000



What is the annual rate of return?



I don%26#039;t understand the equation.



Algebra problem, figuring rate of return.?

Imagine you have $16000. You put it somewhere for a year, and at the end of it, you get $16000 back. You have the same amount of money at the end as you started with, so you would multiply it by 1.



16,000(1) = 16,000



Now imagine you put it somewhere for a year and get 17,600 back. 17,600 is the initial 16,000 plus an additional 1,600 (10% or 0.1). This 0.1 is r



16,000(1 + r) = 16,000(1 + 0.1) = 16,000(1.1) = 17,600



Now imagine you put that 17,600 back in the fund for another year. You would get 10% of that 17,600 back.



i.e. 17,600(1 + r) = 17,600(1 + 0.1) = 17,600(1.1) = 19,360



So in two years you went from 16,000 to 19,360. This was calculated by:



16,000(1 + r) to get 17,600



17,600(1 + r) to get 19,360



This can be simplified to 16,000(1 + r)(1 + r) or 16,000(1 + r)虏 where the square (虏) shows that the initial amount was put into the fund for 2 years.



So the formula for this example would be 16,000(1 + r)虏 = 19,360



Hopefully the above explained how the formula was derived, so I will use the above figures to walk you through a similar question which you can use as a model for your own calculations.



16,000(1 + r)虏 = 19,360



We want to work out what r is, so we need to leave r on its own.



The first thing to do is to get rid of the 16,000 on the left. So we need to divide both sides by 16,000



(1 + r)虏 = 19,360/16,000



(1 + r)虏 = 1.21



We now need to square root both sides to get rid of the square



1 + r = 鈭?.21



1 + r = 1.1



Then just subtract 1 from each side



r = 1.1 - 1



r = 0.1



r = 10% (rate of return is usually given as a percentage)



which is correct, as can be seen from my initial explanation.



IMPORTANT NOTE: THIS IS NOT THE ANSWER TO YOUR QUESTION. THIS IS SIMPLY A WORKED THROUGH ANSWER OF A SIMILAR QUESTION TO SHOW HOW YOU CAN WORK IT OUT YOURSELF.



Algebra problem, figuring rate of return.?

This is a compound interest problem



A = P(1+r)^n



where P is the amount invested, r is the rate of return of the investment and A is the amount after 2 years



16,000(1 + r)虏 = 25,000



(1 + r)虏 = 25000/16000



(1 + r)虏 = 1.5625



1 + r = 1.25



r = 25%



.



Algebra problem, figuring rate of return.?

Assume that the interest is compounded once a year.



You%26#039;ll have to solve for r.



16000(1+r)(1+r)=25000



(1+r)(1+r)=25000/16000=25/16



1+r+r+r^2=25/16



1+2r+r^2=25/16



multiply both sides by 16



16+32r+16r^2=25



16r^2+32r-9=0



you%26#039;ll have to solve this quadratic equation



ar^2+br+c=0



a=16 b=32 c=-9



r=[-b+-sqrt(b^2-4ac)]/2a



solving r=0.25 or -2.25



r is the rate of return and cannot be negative



so r=0.25 or 1/4 or 4 % per year.



I hope you%26#039;re familiar with this.



Algebra problem, figuring rate of return.?

Let r = annual rate of interest, $16,000 and $25,000 are represented by 16 and 25, respectively.



Finding the rate of interest:



16(1 + r)^2 = 25



4(1 + r) = 5



1 + r = 1.25



r = 0.25



Answer: rate of interest per year is 25%



Proof (determine balances per year after interests are added):



1st year:



= $16,000 + 0.25($16,000)



= $16,000 + $4,000



= $20,000



2nd year:



= $20,000 + 0.25($20,000)



= $20,000 + $5,000



= $25,000



Algebra problem, figuring rate of return.?

16000*(1+r)^2 =25000



(1+r)^2=25000/16000



dividing numerator %26amp; denominator in 1000



(1+r)^2=25/16



taking squareroot on both sides



(1+r) = 5/4



r =5/4 -1



r= 1/4



r=.25



r =25%

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