X varies directly with Y and Z. x = 40 when y = 10 and Z = 20. find X when y = 30 and Z = 40.

x = 60

Step-by-step explanation:

Direct variation is of the form

y = kxz

We know x = 40 and y = 10 and z = 20

10 = k * 40 * 20

10 = k * 800

Divide each side by 800

10/800 = k

1/80 = k

The equation becomes

y = 1/80 xz

Let y = 30 and z = 40 and find x

30 = 1/80 * x * 40

30 = 40/80 x

30 = 1/2x

Multiply each side by 2

2 * 30 = 2 * 1/2 x

60 = x