Phyllis investing 65000 dollars a portion earning a simple i

Phyllis investing 65000 dollars, a portion earning a simple interest rate of 5 percent per year and the rest earning a rate of 7 percent per year. After one year the total interest earned on theses investments was 3930 dollars. How much money did she invest at each rate?

At rate 5 percent:

At rate 7 percent:

Solution

Let x amount be invested at 5%

Remaining ( 65000-x) at 7%

Simple interest = principla*rate*time/100

S.I. (1 ) = x*5*1/100 = 0.05x

S.I.(2) = (65000 -x)7*1/100 =(65000-x)).07x

Sum of intersest on one year :

0.05x + (65000-x)).07x = 3930

so,   -0.02x = -620

x = $31000 invested at 5%

and Remaining $ 34000 invested at 7% intersest