Respuesta :
Answer: She invested $12000 at 9% and $6000 at 5%
Step-by-step explanation:
Let x represent the amount which she invested in the account paying 9% interest.
Let y represent the amount which she invested in the account paying 5% interest.
Susan invests 2 times as much money at 9% as she does at 5%.. This means that
x = 2y
The formula for determining simple interest is expressed as
I = PRT/100
Considering the account paying 9% interest,
P = $x
T = 1 year
R = 9℅
I = (x × 9 × 1)/100 = 0.09x
Considering the account paying 5% interest,
P = $y
T = 1 year
R = 5℅
I = (y × 5 × 1)/100 = 0.05y
If her total interest after 1 year is $1380, it means that
0.09x + 0.05y = 1380 - - - - - - - - - -1
Substituting x = 2y into equation 1, it becomes
0.09 × 2y + 0.05y = 1380
0.18y + 0.05y = 1380
0.23y = 1380
y = 1380/0.23
y = 6000
x = 2y = 2 × 6000
x = 12000
