An investment is of $4,600 is made at an annual simple interest rate of 6.8%

Question

An investment is of $4,600 is made at an annual simple interest rate of 6.8%.How much money must be invested at an simple interest rate of 9% so that the total interest earned is 8% of the total investment?

Answer 1

Osaruname,

 

You did not provide a maturity date but that's fine. If it can be answered for one year, which is what I am about to do, it can be answer for any date of maturity. 

 

Earning from the $4,600 = 4600(6.8/100) = $312.80

x = the amount of money invested at an simple interest rate of 9%

y = Earning from the money invested at an simple interest rate of 9% = x(9/100)

z = earning from both x and y = 312.8 + x(9/100)------------- eq(1)

% earning from the other investment at 9% and the 6.8% combined = [z/(x+4600)]*100 = 8------ eq(2)

Take z from eq(1) substitute it for z in eq(2) and solve for x.

I hope this helps