Tom has a large photo he wants to shrink to wallet sized it's with is 20 cm and its length is 30 cm. If he wants the width to be 5 cm what should the length be?
The width was 20 cm and was brought down to 5 cm, you can see that the pictures width was shrunk down 4 times because 20 divide by 4 is 5 so to find the length you would divide 30 by 4 and get 7.5 cm as your answer.
