Please help solve math word problem in description below

Question

Film Frames are 70 millimeters wide and projected on a screen that is up to 99 feet wide. If a 4 millimeter long ant walked onto the film and was projected, how wide would the ant appear on a 99 foot wide screen?

Answer 1

Hi Sandy;

(70 mm)/(99 feet)=(4 mm)/x

Let's note that the unit of mm is in the numerators of both sides.  It cancels...

(70 mm)/(99 feet)=(4 mm)/x

70/(99 feet)=4/x

The only unit remaining is feet.  This is what we want...

Cross-multiply...

70x=(4)(99 feet)

70x=396 feet

Divide both sides by 70...

(70x)/70=(396 feet)/70

x≈5.66 feet