Question

Find an equation of variation where y varies jointly as x and the square of z, and where y=70, when x=21 and z=5.

Answer 1

Answer:

$y = 181.75xz^2$

Step-by-step explanation:

Given

y jointly varies to x and z^2

Required

Find the equation

We start by writing out the variation;

$y\ \alpha\ xz^2$

Write as equation

$y = kxz^2$

Substitute values of x,y and z

$70 = k * 21 * 25^2$

$70 = k * 21 * 25 * 25$

$70 = k * 13125$

Divide both sides by 7

$\frac{70}{13125} = \frac{k * 131251}{13125}$

$\frac{70}{13125} = k$

$187.5 = k$

$k = 181.75$

Substitute k in $y = kxz^2$

$y = 181.75xz^2$