# Direct Variation

Direct variation is a special relationship between two variables. Suppose you have a recipe for a salad giving the measures of various ingredients required, which can serve four people. If you want to prepare the salad for a small party consisting of eight people, how would you alter the measurements of the ingredients for the preparation? Yes, you are correct! The number of people to be served 8 is twice the number servings for which the recipe is given. You will use twice the quantity given for each ingredient, as you have to prepare twice the amount of salad for which the recipe is given. If the measure of cooked mushrooms is given in the recipe as two cups you would use four cups of cooked mushrooms for your preparation. We increase the measurements proportionate to the servings required.

The relationship between the number of servings required 's' and the number of cups of cooked mushrooms used in the salad "c" as s = 2c.This relationship is known as direct variation as the variable s vary the same way as c. For any set of values for s and c, the ratio $\frac{s}{c}$ is a constant and equal to 2.