10) Enlarging by a factor of 7 corresponds to an increase by a factor of 
for the area, or 49. The new rectangle has area 980 square-inches.
To verify, let's say the dimensions of the original rectangle are
. We increase each dimension by a factor of 7 to get 
. This new area is 980 square-inches.
11) We use the same concept. Increasing by a factor of 0.6 corresponds to increasing the area by
(n.b., an increase by a factor less than 1 is shrinking). Original area is 
. New area is 
.
12) We multiply 15 by 11/30 to get 5.5 ft. We multiply 8.25 by the same factor to get 3.025 ft. The area is
.
To verify, let's say the dimensions of the original rectangle are
11) We use the same concept. Increasing by a factor of 0.6 corresponds to increasing the area by
12) We multiply 15 by 11/30 to get 5.5 ft. We multiply 8.25 by the same factor to get 3.025 ft. The area is