Mr. and Mrs. Quigley just moved into a new home with a lot of land. They need to plant grass seed. The problem is that they are not sure how to figure the new amount that they need. At their old house, they knew that the lawn was 10 ft. by 20 ft. and needed 5 pounds of seed. Their new lawn is 100 ft. by 50 ft. How will knowing the amount of seed needed from their old house help them with buying seed for the new lawn?