Math Problem Statement

Suppose z varies directly with x and inversely with the square of y. If z = 24 when x = 6 and y = 5, what is z when x = 12 and y = 10?

Solution

To solve this problem, let's analyze the information given.

  1. Relationship Given:

    • zz varies directly with xx and inversely with the square of yy.
    • This can be expressed as: z=kxy2z = k \cdot \frac{x}{y^2} where kk is a constant of proportionality.
  2. Find kk:

    • We are given that z=24z = 24 when x=6x = 6 and y=5y = 5.
    • Substitute these values to solve for kk: 24=k65224 = k \cdot \frac{6}{5^2}
    • Simplify the equation: 24=k62524 = k \cdot \frac{6}{25}
    • Multiply both sides by 256\frac{25}{6}: k=24256=100k = 24 \cdot \frac{25}{6} = 100

    So, k=100k = 100.

  3. Use kk to Find zz When x=12x = 12 and y=10y = 10:

    • Substitute x=12x = 12, y=10y = 10, and k=100k = 100 into the formula: z=10012102z = 100 \cdot \frac{12}{10^2}
    • Simplify: z=10012100=12z = 100 \cdot \frac{12}{100} = 12

Answer:

z=12z = 12

Would you like a further breakdown of the solution or have any questions?


Here are five related questions for further practice:

  1. If zz varies directly with xx and inversely with yy, how would the equation change?
  2. Suppose zz varies inversely with both xx and the square of yy. How would the equation be modified?
  3. What happens to zz if xx is doubled and yy remains the same?
  4. How would you interpret the proportional constant kk in terms of real-world applications?
  5. If z=48z = 48 when x=8x = 8 and y=4y = 4, what is the value of kk?

Tip: Always determine the constant of proportionality kk first using the initial conditions before applying it to other values.

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Math Problem Analysis

Mathematical Concepts

Direct Variation
Inverse Variation
Proportionality

Formulas

z = k * (x / y^2)

Theorems

Direct and Inverse Variation

Suitable Grade Level

Grade 10