A rectangular photograph is mounted on a rectangular card. There is a border ofequal width around the photograph. The perimeter of the card is 40 centimeters longer than that of the photograph. Find the width of the border in centimeters.

1 answer

Let the width of the border be x cm. Since you are given a correlation between 2 different-sized perimeters, you will have to add 8 of the widths together:
8x = 40
x = 5 cm

Drawing it out will help.