Suppose Y varies directly with X, and Y = 15 and X = 5. Write a direct variation equation that relates X and Y. What is the value of Y when X = 9?

Step-by-step explanation:

If two variables are directly proportional, it means that an increase in the value of one variable would cause a corresponding increase in the other variable. Also, a decrease in the value of one variable would cause a corresponding decrease in the other variable.

Given that Y varies directly with X, and Y = 15 and X = 5, if we introduce a constant of proportionality, k, the expression becomes

15 = 5k

k = 15/5

k = 3

The equation would be

Y = 3X

Therefore, when X = 9, the value of Y would be

Y = 3 * 9

Y = 27