2.( 1) side: 3.14× 4 = 3.14×16 = 50.24 (cm? ﹚

Table: 3. 14×2? ×2﹢50.24=8×3. 14+50.24=75.36﹙cm？ )

-2 sides: 3.14× 3× 2×12 = 226.08-cm? )

Table: 3. 14×3? ×2+226.08 = 3. 14× 18+226.08 = 282.6(cm？ )

3、94.2× 10+[﹙94.2÷3. 14÷2﹚? ×3. 14×2]=942+﹙225×6.28﹚=942+ 14 13=2355﹙cm？ )

4、﹙ 1﹚3. 14×8× 10=3. 14×80=25 1.2﹙cm？ )

(2)8÷2=4 cm

25 1.2+(4? ×3. 14)×2 = 25 1.2+ 100.48 = 35 1.68(cm？ )

5、3. 14×3×2+﹙3÷2﹚? ×3. 14×2=32.97(dm？ )

3. 14×2×2+﹙2÷2﹚? ×3. 14×2= 18.84(dm？ )

32.97+ 18.84-(2÷2)? ×3. 14×2=45.53(dm？ )

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