2、? Great circle radius = 3cm and small circle radius = 2cm；; Great circle circumference =18.84cm; Small circumference = 6.28cm.

3、? 2 pieces: diameter ×2+ circumference × 1

3 pieces: diameter ×4+ circumference × 1

4 pieces: diameter ×6+ circumference × 1

Rule: (number-1)×2+ perimeter × 1

4、? Diameter or circumference

5、? (1) The first route is A-B-C-D-E, 50×2+ 100=200.

The second route is A-C-E 50×3, 14= 157.

(2)200- 157=43

6、 3. 14×2+3. 14×4÷2= 12.56

Or 3. 14 ×4= 12.56.

7、 3. 14× 12÷4=0.785