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5. Z varies jointly as x and y. If z=3 when x=3 and y=15, find z when x=6 and y=9

Sagot :

z varies jointly as x and y. If z=3 when x=3 and y=15, find z when x=6 and y=9

Equation

[tex] z = kxy \\ [/tex]

Evaluate the first given values (z=3, x=3 and y= 15)

[tex]3 = k(3)(15) \\ [/tex]

Multiply 3 to 15

[tex] 3 = k(45) \\ [/tex]

Divide both sides by 45

[tex] \frac{3}{45} = \frac{k(45)}{45} \\ [/tex]

Cancel both 45 from the right side

[tex] \frac{3}{45} = \frac{k( \cancel{45})}{ \cancel{45}} \\ [/tex]

Simplify

[tex] k = \frac{1}{15} \\ \\ [/tex]

Now, find the value of z when x= 6 and y= 9. Use 1/15 for the value of the constant of variation (k).

Equation

[tex] z = kxy \\ [/tex]

Evaluate the values

[tex] z = ( \frac{1}{15} )(6)(9) \\ [/tex]

Multiply

[tex] z = ( \frac{1}{15} )(6)(9) \\ z = ( \frac{2}{5} )(9) \: \: \: \: \: \: \: \: \: \\ \green{\boxed{ \boxed{ \: \: \: \: \: \: z = \frac{18}{5} \: \: \: \: \: \: }}} \\ \\ [/tex]