0 : 0251 x
0 : 0251
¼
80
0 : 025
x¼$3200 invested at 4%
5000 x¼ 5000 3200 ¼$1800 invested at 6
1
2
%
EVALUATION: Find the interest on both investments separately and then
add them up to see if they equal $245. UseI¼PRTwhereT¼1.
First investment:I¼$ 3200 ð 4 %Þ¼$ 128
Second investment:I¼$ 1800 ð 6
1
2
%Þ¼$ 117
$ 128 þ$ 117 ¼$ 245
EXAMPLE:A person has twice as much money invested at 6% as he has at
3%. If the total annual interest from the investments is $315, how much does
he have invested at each rate?
SOLUTION:
GOAL: You are being asked to find how much money is invested at 6%
and 3%.
STRATEGY: Letx¼the amount of money invested at 3% and 2x¼the
amount of money invested at 6%; then
Principal Rate ¼ Interest
First investment 2 x 6% 6%(2x)
Second investment x 3% 3%(x)
The equation is 6%(2x)þ3%(x)¼$315.
IMPLEMENTATION: Solve the equation:
0 : 06 ð 2 xÞþ 0 : 03 ðxÞ¼ 315
0 : 12 xþ 0 : 03 x¼ 315
162 LESSON 15 Solving Finance Problems