If y varies directly as x and we know that y is 6 when x is 72, what is the value of y when x is 8?

To solve the problem, we start by understanding the concept of direct variation. When we say that y varies directly as x, it means that there is a constant ratio between y and x. This relationship can be expressed mathematically as:

y = kx

Where k is the constant of variation. To find the value of k, we can use the initial given values of y and x.

Given:

  • y = 6
  • x = 72

Substituting these values into the direct variation equation:

6 = k * 72

To isolate k, we divide both sides by 72:

k = \frac{6}{72} = \frac{1}{12}

Now that we have the value of our constant k, we can use it to find the value of y when x is 8. We substitute x = 8 into the direct variation equation:

y = kx

Substituting for k:

y = \frac{1}{12} * 8

Now, we can calculate:

y = \frac{8}{12} = \frac{2}{3}

Thus, the value of y when x is 8 is:

y = \frac{2}{3}

In summary, when x is 8, the value of y is two-thirds (or approximately 0.67).

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