Carmen has a sign with dimensions 5 ft × 7.5 ft. She wants to reduce it to make a postcard. Postcard sizes are 3.5 in. × 5 in., 4 in. × 6 in., and 4.25 in. × 6 in. Which size postcard should she use? Explain.

The size of the post card she should use is 4 in. × 6 in.

Step-by-step explanation:

The parameters given are;

Dimensions of sign = 5 ft. × 7.5 ft

Hence, the ratio of the side sizes are;

5:7.5 which is the same as 2:3, therefore, to obtain the most accurate design of the sign on the post card, the size of the post card must be in direct proportion to the size of the sign which gives;

Side length ratio of post card = 2:3 = 4:6 = 4 in. × 6 in.

The size of the post card she should use is therefore = 4 in. × 6 in.