| 3 |
| 7 |
| 3 |
| 8 |
（2）200.5×10%+2.005×490+0.2005×5000
（3）3333×3333+9999×8889
（4）
| 1 |
| 1×4 |
| 1 |
| 4×7 |
| 1 |
| 7×10 |
| 1 |
| 97×100 |
（5）若3.5×[6.8-（1.6+△÷0.9）÷8.4=0.5，求△的值．（1））（111+999）÷[56×（
| 3 |
| 7 |
| 3 |
| 8 |
=1110÷[56×
| 3 |
| 7 |
| 3 |
| 8 |
=1110÷[24-21]
=1110÷3
=370
（2）200.5×10%+2.005×490+0.2005×5000
=20.05×1+20.05×49+20.05×50
=2005
（3）3333×3333+9999×8889
=1111×9999+9999×8889
=9999×10000
=99990000
（4）
| 1 |
| 1×4 |
| 1 |
| 4×7 |
| 1 |
| 7×10 |
| 1 |
| 97×100 |
=（1-
| 1 |
| 4 |
| 1 |
| 4 |
| 1 |
| 4 |
| 1 |
| 7 |
| 1 |
| 10 |
| 1 |
| 97 |
| 1 |
| 100 |
| 1 |
| 3 |
=
| 99 |
| 100 |
| 1 |
| 3 |
=
| 33 |
| 100 |
（5）由3.5×[6.8-（1.6+△÷0.9）÷8.4=0.5，
可知3.5×[6.8-（1.6+△÷0.9）=0.5×8.4=4.2，
6.8-（1.6+△÷0.9）=4.4÷3.5=1.2，
（1.6+△÷0.9）=6.8-1.2=5.6
△÷0.9=5.6-1.6=4，
△=4×0.9=3.6．