1、(1)两;三 (2) 4.996;5.00;5.0
2、< > > = < <
3、题目略
(1) 74 (2) 39.9 (3) 2.996
(4) 398.72 (5) 0.1104 (6) 380.7
4、题目略
(1) 90 (2) 9.75
(3) 1990 (4) 99.9
5、题目略
(1) 18.6×4.5=83.7
(2) (4.25-0.9)×0.8=2.68
6、题目略
(1) 38.8×4.1=159.08≅159(吨)
(2) 1.2×1.5 ×2.3 =4.14=4.1(吨)
(3) 45.5×(2+1)×2=273(米)
(4) 3.8×0.45=1.71(千克),120×1.71=205.2(千克)