Question

A scale drawing has a scale of 1/4in:12ft. Find the length on the drawing for each actual length. 15 ft.

Answer 1

So the ratio is at ¼ : 12, namely the drawing has ¼ inch to an actual 12 feet.

so, what would it be for an actual 15 feet on the drawing then?

$\bf \begin{array}{ccll} \stackrel{inches}{drawing}&\stackrel{feet}{actual}\\ \text{\textemdash\textemdash\textemdash}&\text{\textemdash\textemdash\textemdash}\\ \frac{1}{4}&12\\\\ d&15 \end{array}\implies \cfrac{\quad \frac{1}{4}\quad }{d}=\cfrac{12}{15}\implies \cfrac{\quad \frac{1}{4}\quad }{\frac{d}{1}}=\cfrac{12}{15} \\\\\\ \cfrac{1}{4}\cdot \cfrac{1}{d}=\cfrac{12}{15}\implies \cfrac{1}{4d}=\cfrac{12}{15}\implies 15=48d\implies \cfrac{15}{48}=d\implies \cfrac{5}{16}=d$