If he invests $4000 at 4% int./yr,how much additional$$ must he invest at 5.5% annual int. to ensure that the int. he receives per year is 4.5% of total amount

Question

modeling with the 4 steps, find variable 

Answer 1

I = prt

 

We want our interest to be 4.5% of the original amount

4000(.045) = 180

 

Our variable "x" is the amount of money to be invested at 5.5%.

The total interest will be the sum of the interest on $4000 at 4% and $x at 5.5%.

 

180 = 4000(.04)(1) + .055x(1)

180 = 160 + .055x

20 = .055x

x = 20/.055

x = $363.64