A scale drawing of a building has the scale of 0.5 inches : 6 feet. A wall is 30 feet long. How many inches long will the wall be on the drawing?

The wall will be ##2 1/2## inches long on the drawing

Using ratio:

Write 0.5 inches to 6 feet as:

##" "0.5/6##

Let the unknown scale down size be ##x##

Then we have:

##" "color(brown)(0.5/6=x/30)##

To get ##x## on its own multiply both sides by 30

##color(brown)(0.5/6=x/30)" "->" "color(brown)(color(blue)(30xx)0.5/6" "=" "(color(blue)(30))/30 xx x)##

But ##30/30=1##

##" "(30xx0.5)/6=1xx x##

##" "x=2 1/2##