1.8× 3.14 = 25.12 (decimeter) 8 ÷ 2 = 43.14×16 = 50.24 (square decimeter).

2.47 . 1÷3. 14 = 15(m)？ 15÷2=7.5? 3.14× 56.25 =176.625 m2

3.25× 3.14 = 78.5m2.

4. 10÷2=5? 12-5=7? 49×3. 14= 153.86 (square centimeter)

5.12×12× 3.14-8× 8× 3.14 = 251.2 (square centimeter)

6.20.56÷5. 14=4 ? 16×3. 14=50.24 (square centimeter)

7.