1) 21^ + 18^2 = 756km^2 approx 27.7 km
2) 11^2 - 8^2 = 57cm^2 approx 7.55 cm
3) 13^2 + 7^2 = 216feet^2 approx 14.8 feet
4) 51^2 - 29^2 = 1760feet^2 approx 42 feet
5) 12^2 + 21^2 = 585feet^2 approx 24.2 feet
6) 18^2 + 10^2 = 424cm^2 approx 20.6 cm
7) 12^2 + 8^2 = 208cm^2 approx 14.4 cm
8) 14^2 - 5^2 = 171feet^2 approx 13.1 feet
9) 19^2 - 15^2 = 136cm^2 approx 11.7 cm
