How do you derive the equation that describes the relationship where y varies jointly with w and x, and inversely with z, given that y is 360 when w is 8, x is 25, and z is 5?

To determine the equation that models the relationship between the variables y, w, x, and z, we start by understanding the principle of joint and inverse variation.

When we say that y varies jointly with w and x, it means that y is proportional to the product of w and x. Additionally, since y varies inversely with z, it means that y is also inversely proportional to z.

Combining these relationships gives us the following equation:

y = k * (w * x) / z

Here, k is the constant of proportionality that we need to determine.

Given the values:

  • w = 8
  • x = 25
  • z = 5
  • y = 360

We can substitute these values into the equation to solve for k:

360 = k * (8 * 25) / 5

First, calculate the product on the right side:

  • 8 * 25 = 200

Now simplify the equation:

360 = k * (200 / 5)

Now calculate 200 divided by 5:

  • 200 / 5 = 40

This gives us:

360 = k * 40

To find k, divide both sides by 40:

k = 360 / 40

Calculating this gives:

  • k = 9

Now that we have determined k, we can substitute it back into our initial equation:

y = 9 * (w * x) / z

This is the equation that models the relationship where y varies jointly with w and x, while inversely with z.

In conclusion:

The final equation is:

y = 9 * (w * x) / z

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