Simple Interest

Question

Katie invested a total of $5,000.00, part at 3% simple interest and part at 4% simple interest. At the end of 1 year, the investments had earned $171.00 interest. How much was invested at each rate?

 

Answer 1

let consider

Kelvin invested amount x at 3 %

and amount (5000-x) in at 4 %

 

interest earned at 3% = x*3%=x*0.03=0.03x

interest earned at 4 %= (5000-x)* 4%=(5000-x)0.04=200-0.04x

 

At the end of 1 year, the investments had earned $171.00 interest

 

0.03x+200-0.04x=171

 

-0.01x =-29

 

x=2900

 

Kelvin invested amount x at 3 % =$2900
and amount (5000-x) in at 4 % =$5000-2900=$2100

Answer 2

simple interest:  I = prt

 

let x = amount invested at 3%

The 5000-x = amount invested at 4%

 

The total interest earned is the sum of

the amount earned at each rate.

 

171 = .03x + .04(5000-x)

 

Solve for x to determine how much was

invested at 3%