What is the value of Z when X = 10

Question

variable Z is directly proportional to X. When X is 6, Z has the value 18.

Answer 1

variable Z is directly proportional to X means Z = kX.

 

When x = 6, Z = 18 tells us 18 = k(6), from which we conclude k = 3.

 

So we know Z = 3X.

 

Now substitute X = 10 to find Z.