Don invested $4000, part at 5% interest and the rest at 9%. Find how much he invested at each rate if the total interest after one year is $311.
2006-10-16 13:22:45 · 11 answers · asked by Anonymous in Science & Mathematics ➔ Mathematics
.05x+(4000-x)*.09=311
.05x+360-.09x=311
-.04x=-49
x=49/.04=$1225 at 5% &
4000-1225=$2775 at 9%
check
1225*.05+2775*.09= 61.25 +249.75=$311
2006-10-16 13:29:10 · answer #1 · answered by yupchagee 7 · 16⤊ 1⤋
Hi. When you invest money and it grows because of interest, it increases by that given percent (usually per year).
For example, if 10 dollars is invested at 2%, by one year it is 10 + 0.2*10 = 10(1+.2) = 10(1.2) = 12.
So, what you have here is a classic system of equations, two equations with two variables.
Let f, n be the variables meaning the amount invested at 5 percent and nine percent respectively.
therefore:
0.05f + 0.09n = 311
and because the total is 4000,
f + n = 4000.
I will leave the solving of these equations up to you.
2006-10-16 20:29:04 · answer #2 · answered by animal 2 · 0⤊ 0⤋
Let's call the share invested at 5%, f and the share at 9%, n. Now,
1) f + n = $4000
We also know that the interest after one year is $311. So,
2) 0.05f + 0.09n = $311
Solve the system to get
f = $1225
n = $2775
2006-10-16 20:30:00 · answer #3 · answered by Dochar 2 · 0⤊ 0⤋
Solve this system of linear equations, and you've got it.
X+Y=4000
.05X+.09Y=311.
X represents the part invested at 5%, and Y the part at 9%. They total 4000, and the total interest is $311.
I'm guessing (I haven't solved it) that there is more Y than X--about 2500, 1500.
2006-10-16 20:27:21 · answer #4 · answered by zex20913 5 · 0⤊ 0⤋
X(.05) + [4000-X](.09) = 311
solve for X, thats the amount at 5%,
4000-X is the amount at 9%.
2006-10-16 20:27:33 · answer #5 · answered by davidosterberg1 6 · 0⤊ 0⤋
The problem cannot be solved until you add information such as wether ther interest rates are per annum, per month etc...
If a flat per annum rate is assumed then others have already given you the answer.
2006-10-16 20:31:47 · answer #6 · answered by StatIdiot 5 · 0⤊ 0⤋
Set up a system of equations:
a(.05) + b(.09) = $311
a+b = $4000
Therefore a= 4000 -b
(4000)(.05) - .05b +.09b = 311
4000(.05) +.04b = 311
200 +.04b = 311
.04b = 111
b = $2775
a = $1225
(check my math to be sure)
2006-10-16 20:29:35 · answer #7 · answered by Barkus109 2 · 0⤊ 0⤋
at .05 rate 1225 at .09 rate 2775
2006-10-16 20:35:09 · answer #8 · answered by Buckeye 1 · 0⤊ 0⤋
$2775 @ 9%
$1225 @5%
2006-10-16 20:38:27 · answer #9 · answered by Pablo M 2 · 0⤊ 0⤋
o, i know that one, its....5!!
2006-10-16 20:29:32 · answer #10 · answered by Brittany R 3 · 0⤊ 0⤋