If 800ml of a juice drink is 15% grape juice, how much should be added to make a drink that is 20% grape juice?
To solve this problem, you need to use the concept of mixture problems.
Step 1: Understand the problem
You have 800ml of a juice drink that contains 15% grape juice. You want to know how much grape juice needs to be added to make a drink that is 20% grape juice.
Step 2: Set up the equation
Let's assume that you need to add x ml of pure grape juice to the existing 800ml drink. The total volume of the new drink will be (800 + x) ml. Since the grape juice being added is pure, it will be 100% grape juice.
The equation can be set up as follows:
(800 * 0.15) + (x * 1) = (800 + x) * 0.20
Step 3: Solve the equation
Now, you can solve the equation to find the value of x.
Using the equation from step 2, we can simplify it as:
120 + x = 160 + 0.20x
Rearranging the equation:
0.20x - x = 160 - 120
0.80x = 40
Dividing both sides by 0.80:
x = 40 / 0.80
x = 50
Therefore, you need to add 50ml of pure grape juice to the existing 800ml drink to make a drink that is 20% grape juice.