Question 891538:  This problem has three questions with it, im sorry.  
You plan to invest some money in an account paying simple intrest. What intrest rate do you need if you invest $1500, and want to end up with a total of $1800 after two years? 
 
How much do you need to invest if the intrest rate is 5%, and you need a total of $1800 in 4 years? 
 
How long do you need to wait to have a total of $2000 if you invest $1600 at 5% intrest?  
 Answer by ankor@dixie-net.com(22740)      (Show Source): 
You can  put this solution on YOUR website! The simple interest formula: I = PRT, where: 
I = interest earned 
P = principal (initial amt) 
R = Interest rate in decimal form 
T = time in years 
: 
 What intrest rate do you need if you invest $1500, and want to end up with a total of $1800 after two years? 
Amt of interest (I) is 1800-1500 = 300, find R 
300 = 1500*R*2 
300 = 3000R 
R = 300/3000 
R = .10 which is 10% 
: 
How much do you need to invest if the intrest rate is 5%, and you need a total of $1800 in 4 years? 
Find P 
300 = P*.05*4 
300 = .2P 
P = 300/.2 
P = $1500 
: 
How long do you need to wait to have a total of $2000 if you invest $1600 at 5% 
 intrest?  
Interest earned here: 2000-1600 = 400 
400 = 1600*.05*T 
400 = 80T 
T = 400/80 
T = 5 yrs 
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