If y varies directly with x and if x is 75 when y is 10, how do you find x when y is 4?

To solve this problem, we need to understand the concept of direct variation. When we say that y varies directly with x, it means that there is a constant ratio between y and x. We can express this relationship with the equation:

y = kx

Here, k is the constant of variation. From the information provided, we know:

  • x = 75 when y = 10

First, we can find the value of k by substituting these values into the equation:

10 = k * 75

To solve for k, we divide both sides by 75:

k = 10 / 75

Now, simplifying that:

k = 2 / 15

Now that we have the value of k, we can use it to find the value of x when y = 4:

Substituting into the direct variation equation:

4 = (2 / 15) * x

To find x, we can multiply both sides by the reciprocal of (2/15), which is (15/2):

x = 4 * (15 / 2)

Calculating that:

x = 60

So when y is 4, the corresponding value of x is 60. Therefore, in summary, the answer is:

x = 60

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