Question 20
Over the last 20 years, the standard ratio of television screens has changed from 4 : 3 to 16 : 9. When the ratio of content does not match the ratio of the screen it is being viewed on, black bars are often used to compensate, as illustrated. The left diagram is a 4 : 3 image on a 16 : 9 screen; the right is a 16 : 9 image on a 4 : 3 screen. If ℓ is the fraction of the screen blacked out in the left diagram, and r is the fraction blacked out in the right diagram, then the ratio ℓ : r equals
