Answer:
The amount invested at 4% is $20,500 and the amount invested at 10% is $500
Step-by-step explanation:
Let
x -----> the amount invested at 4%
(21,000 -x) ----> the amount invested at 10%
we know that
The interest of the amount invested at 4% plus the interest of the amount invested at 10% must be equal to $870
[tex]4\%=4/100=0.04[/tex]
[tex]10\%=10/100=0.10[/tex]
so
[tex]0.04(x)+0.10(21,000-x)=870[/tex]
Solve for x
[tex]0.04x+2,100-0.10x=870[/tex]
[tex]0.10x-0.04x=2,100-870[/tex]
[tex]0.06x=1,230[/tex]
[tex]x=\$20,500[/tex]
[tex]21,000-x=\$500[/tex]
therefore
The amount invested at 4% is $20,500 and the amount invested at 10% is $500
