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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.\newlineThe general form of joint variation is z=k×xn×ymz = k \times x^n \times y^m, where kk is the constant of proportionality, nn and mm are the powers to which xx and yy are raised, respectively.\newlineIn this case, since zz varies jointly with the cube of xx and the square of yy, the equation becomes z=k×x3×y2z = k \times x^3 \times y^2.
  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^2.3600=k×53×323600 = k \times 5^3 \times 3^2
  3. Calculate x3x^3 and y2y^2: Calculate the values of x3x^3 and y2y^2.\newline53=1255^3 = 125\newline32=93^2 = 9
  4. Substitute calculated values: Substitute the calculated values back into the equation. 3600=k×125×93600 = k \times 125 \times 9
  5. Solve for constant: Solve the equation for the constant of proportionality, kk.3600=k×11253600 = k \times 1125k=36001125k = \frac{3600}{1125}k=3.2k = 3.2
  6. Write joint variation equation: Write the joint variation equation using the value of kk.\newlineSubstitute k=3.2k = 3.2 into z=k×x3×y2z = k \times x^3 \times y^2.\newlineThe joint variation equation is z=3.2×x3×y2z = 3.2 \times x^3 \times y^2.
  7. Find zz with new values: Find zz given that y=12y = 12 and x=13x = 13 using the joint variation equation.\newlineSubstitute y=12y = 12 and x=13x = 13 into z=3.2×x3×y2z = 3.2 \times x^3 \times y^2.\newlinez=3.2×133×122z = 3.2 \times 13^3 \times 12^2
  8. Calculate 13313^3 and 12212^2: Calculate the values of 13313^3 and 12212^2.\newline133=219713^3 = 2197\newline122=14412^2 = 144
  9. Substitute values for z: Substitute the calculated values back into the equation to find z.\newlinez=3.2×2197×144z = 3.2 \times 2197 \times 144
  10. Perform multiplication: Perform the multiplication to find the value of zz.z=3.2×316,608z = 3.2 \times 316,608z=1,013,145.6z = 1,013,145.6

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