Question 164032
Consider this!
You want to find how much of Walt's $9,000.00 was invested at 8%.
Call this amount x dollars.
The interest earned on this amount would then be 8% of x, or 0.08x.
The remainder of Walt's $9,000.00, that's ($9,000-x) was invested at 9%.
The interest earned on this amount would be 9% of ($9000.00-x) or 0.09($9000.00-x).
The sum of these two amounts of interest is $770.00, so we can write the equation to find x.
0.08x+0.09($9000.00-x) = $770.00 Simplify this and solve for x.
0.08x+$810.00-0.09x = $770.00 Combine like-terms.
-0.01x+$810.00 = $770.00 Subtract $810.00 from both sides.
-0.01x = - $40.00 Divide both sides by 0.01
x = $4000.00
Walt invested $4000.00 at 8% interest.
Check:
0.08($4000.00)+0.09($5000.00) = $320.00+$450.00 = $770.00