story problem

Question

An investment club used funds totaling $250,000 to invest in a bio-tech company and in an ethanol plant, with hopes of earning 11% and 15% annual simple interest, respectively. Their hunch paid off. The club made a total of $30,700 interest the first year. How much was invested at each rate?

Answer 1

Let's say x is the amount invested at 11% 

Let's say y is the amount invested at 15%

 

So you can set up two equations,

x + y = 250000

.11x + .15y = 30700

 

I usually get rid of the decimals by multiplying by 100

 

x + y = 250000 

11x + 15y = 3070000

 

multiply the first equation by -11 so the xs will cancel

 

-11x -11y = -2750000

11x + 15y = 3070000     add these to get

 

4y        = 320000

y           = 80000

 

Substituting back in

x + 80000 = 250000..........so x = 170000

 

Hope this helps.