Question

Suppose y varies directly with x, and y = 25 when x = 5. What is the value of y when x = 7 ?

Answer 1

35

Explanation:

y = 25 and x = 5

When two variable quantities have a constant ratio their relationship is called a direct variation. The formula for direct variation is y = kx, where k is called the constant of variation. If we know k we can find y given x or we can find x given y.

If we solve the equation y = kx for k, we get k = y/x. If we replace the variables x and y with the actual values from the problem we have:

k = 25/5, which is 5.

Now we can substitute this value for k into the equation y = kx to find y when x is 7:

y = (5) (7)

y = 35