Question

The variable z is directly proportional to r. When x is 18, z has the value 216.

What is the value of z when 2 = 26?

Answer 1

z=312 if you meant x=26

Explanation:

Direct proportional means there is a constant k such that z=kr. k is called the constant of proportionality. The constant k will never change no matter your (x,z).

So using our equation z=kr with point (18,216) we will find k.

216=k(18)

Divide both sides by 18

216/18=k

k=216/18

Simplify

k=12

So we now know the equation fully that satisfies the given conditions of directly proportion and goes through (x,z)=(18,216).

It is z=12x.

Now we want to know the value of z if x=26.

Plug it in. z=12(26)=312

z=312