Question

Y varies jointly as x and z. y equals 70 when x equals 7 and z equals 2. Find y when x equals 6 and z equals 4.

y= ?

Answer 1

Hello from MrBillDoesMath!

Answer: y = 120

Discussion:

"y varies jointly as x and z" ==> y = k*x*z where k is a constant

Substitute y = 70, x = 7, z = 2 in this equation to determine the value of k

y = k *x * z

70 = k * 7 * 2 or

70 = 14k or

k = 5.

So y = 5 *x * z is the equation of variation.

Substituting x = 6 and z =4 in the equation gives

y = 5 * x * z = 5 * 6 * 4 = 120

Thank you,

MrB