Answer:
$2,400 was placed in the account earning 4%, and $1,600 was placed in the account earning 9%
Explanation:
In this case, we have two unknowns, so in order to be solved, we need to find two equations.
We know that amount 1, that we call x, plus amount 2, we call y, is 4000.
<em>x + y = 4000</em>
Also we know, when we add the interest earned on amount 1 to the interest earned on amount 2, the total interest is 6% of 4000, it means: 240
<em>0.04x+0.09y=240</em>
So, we have two equations with two unknowns
<em>x + y = 4000</em>
<em>0.04x+0.09y=240</em>
That we can solve for any method we know. We will use substitution. Lets clear from first equation the unknown x.
x=4000-y
Then, we substitute in second equation
0.04(4000-y)+0.09y=240
And we solve:
160-0.04y+0.09y=240
0.05y=240-160
y=80/0.05=1600
Now we simply plug this into our first equation and solve for x
x+y=4000
x+1600=4000
x=4000-1600
x=2400
So, $2,400 was placed in the account earning 4%, and $1,600 was placed in the account earning 9%
