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Suppose that zz varies jointly with the cube of xx and the square of yy. Find the constant of proportionality kk if z=3600z = 3600 when y=3y = 3 and x=5x =5. Using the kk from above write the variation equation in terms of xx and yy. Using the kk from above find zz given that x=x=1212 and x=x=1313.

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Q. Suppose that zz varies jointly with the cube of xx and the square of yy. Find the constant of proportionality kk if z=3600z = 3600 when y=3y = 3 and x=5x =5. Using the kk from above write the variation equation in terms of xx and yy. Using the kk from above find zz given that x=x=1212 and x=x=1313.
  1. Identify General Form: Identify the general form of joint variation.\newlineJoint variation is when one variable varies directly as the product of two or more other variables. The general form of joint variation with the cube of xx and the square of yy is z=k×x3×y2z = k \times x^3 \times y^2, where kk is the constant of proportionality.
  2. Substitute Values into Equation: Substitute z=3600z = 3600, y=3y = 3, and x=5x = 5 into the equation z=k×x3×y2z = k \times x^3 \times y^2.\newline3600=k×53×323600 = k \times 5^3 \times 3^2
  3. Solve for Constant: Solve the equation for the constant of proportionality, kk.3600=k×125×93600 = k \times 125 \times 93600=k×11253600 = k \times 1125k=36001125k = \frac{3600}{1125}k=3.2k = 3.2
  4. Write Joint Variation Equation: Write the joint variation equation using the value of kk found in Step 33.\newlineSubstitute k=3.2k = 3.2 into z=k×x3×y2z = k \times x^3 \times y^2.\newlinez=3.2×x3×y2z = 3.2 \times x^3 \times y^2
  5. Find z with New Values: Use the joint variation equation to find zz when y=12y = 12 and x=13x = 13. Substitute y=12y = 12 and x=13x = 13 into z=3.2×x3×y2z = 3.2 \times x^3 \times y^2. z=3.2×133×122z = 3.2 \times 13^3 \times 12^2
  6. Calculate Final Value: Calculate the value of zz.z=3.2×2197×144z = 3.2 \times 2197 \times 144z=3.2×316368z = 3.2 \times 316368z=1011577.6z = 1011577.6

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