Question

One canned juice drink is 25?% orange? juice; another is 5?% orange juice. How many liters of each should be mixed together in order to get 20 L that is 15?% orange? juice?

Answer 1

Let
`x` be the amount (by volume) of the first juice drink, and
`y` the amount of the second that you will use in the mixture.

We want a mixture of 20 L, so

`x+y=20`

For each liter of the first drink, 0.25 L will be orange juice. For each liter of the second drink, 0.05 L will be orange juice. We want the new mixture to end up with 0.15 L of orange juice for every liter of the mixture, so that

`0.25x+0.05y=0.15(x+y)=3`

Now we solve the system:

`\begin{cases}x+y=20\\0.25x+0.05y=3\end{cases}\implies x=10,y=10`