Question

The variable Z is directly proportional to X. When X is 12, Z has the value 228.

What is the value of Z when X = 18

Answer 1

`\bf \qquad \qquad \textit{direct proportional variation}\\\\ \textit{\underline{y} varies directly with \underline{x}}\qquad \qquad y=kx\impliedby \begin{array}{llll} k=constant\ of\\ \qquad variation \end{array}\\\\ -------------------------------\\\\`


`\bf \textit{\underline{z} is directly proportional to \underline{x}}\qquad z=kx \\\\\\ \textit{we also know that } \begin{cases} x=12\\ z=228 \end{cases}\implies 228=k12\implies \cfrac{228}{12}=k \\\\\\ 19=k\qquad thus\qquad \boxed{z=19x}\\\\ -------------------------------\\\\ \textit{what's \underline{z} when \underline{x} is 18?}\qquad z=19(18)`