To solve this problem we can set up a proportion, letting x represent the unknown amount of cooking oil.
30 milliliters water/20 milliliters cooking oil = x milliliters water/ 50 milliliters cooking oil
30/20 = x/50
To solve this proportion, we can use cross products, also called the means extremes products theorem. This takes the products of the numerator and denominator from the separate fractions and sets them equal to one another. In this circumstance, it results in the equation:
(30)(50) = (x)(20)
When we multiply we get:
1500 = 20x
Finally, we have to divide both sides of the equation by 20 to get our variable x alone on the right side of the equation.
x = 75 milliliters
Therefore, the proportion is completed, as 30/20 = 75/50.
Answer: You need 75 milliliters of water.