Answer: she invested $4000 at 6% and $6000 at 7%
Explanation:
Let x represent the amount which she invested in the account paying 6% interest.
Let y represent the amount which she invested in the account paying 7% interest.
Linda invest a total of $10,000 into 2 savings account, one account to pay 6% interest and the other pays 7%. This means that
x + y = 10000
The formula for determining simple interest is expressed as
I = PRT/100
Considering the account paying 6% interest,
P = $x
T = 1 year
R = 6℅
I = (x × 6 × 1)/100 = 0.06x
Considering the account paying 7% interest,
P = $y
T = 1 year
R = 7℅
I = (y × 7 × 1)/100 = 0.07y
If she receives a total of $660 in interest after one year, it means that
0.06x + 0.07y = 660 - - - - - - - - - -1
Substituting x = 10000 - y into equation 1, it becomes
0.06(10000 - y) + 0.07y = 660
600 - 0.06y + 0.07y = 660
- 0.06y + 0.07y = 660 - 600
0.01y = 60
y = 60/0.01
y = 6000
x = 10000 - y = 10000 - 6000
x = 4000