One more problem I'm having trouble with:
Walt made an extra $7000 last year from a part time job. He invested part of the money at 6% and the rest at 8%. He made a total of $500 in interest. How much was invested at 8%?
Hello, Jerry99!
Here is one way to reason it out . . .
We will use liters of the 30% solution.
. . It contains: . liters of alcohol.
We have liters of the 90% solution.
. . It contains: . liters of alcohol.
The mixture will have: . liters of alcohol. .[1]
But we know that the mixture will be liters which is 40% alcohol.
. . The mixture will have: . liters of alcohol. .[2]
We just described the final amount of alcohol in two ways.
There is our equation! . . .