《2025年口算题卡升级练五年级数学上册人教版》

0.4×2.1=2.1×0.4
0.125×1.3×0.8= (0.125×0.8)×1.3
30.8×10.1= 30.8×(10+0.1)
(12.3×4)×2.5=12.3×(4×2.5)
4.3×9.8= 4.3×(10-0.2)
2.3×(100+2)=2.3×100+2.3×2

答案： 0.4×2.1=2.1×0.4
0.125×1.3×0.8=(0.125×0.8)×1.3
30.8×10.1=30.8×(10+0.1)
(12.3×4)×2.5=12.3×(4×2.5)
4.3×9.8=4.3×(10-0.2)
2.3×(100+2)=2.3×100+2.3×2

用简便方法计算下面各题。
0.78×99+0.78
27.2×101-27.2
3.48×0.5×0.2
0.72×98
102×0.85
10.3×8.3+10.3×1.7
0.125×6.7×8
3.6×99
0.25×24

答案： 0.78×99+0.78
=0.78×(99+1)
=0.78×100
=78
27.2×101-27.2
=27.2×(101-1)
=27.2×100
=2720
3.48×0.5×0.2
=3.48×(0.5×0.2)
=3.48×0.1
=0.348
0.72×98
=0.72×(100-2)
=0.72×100-0.72×2
=72-1.44
=70.56
102×0.85
=(100+2)×0.85
=100×0.85+2×0.85
=85+1.7
=86.7
10.3×8.3+10.3×1.7
=10.3×(8.3+1.7)
=10.3×10
=103
0.125×6.7×8
=0.125×8×6.7
=1×6.7
=6.7
3.6×99
=3.6×(100-1)
=3.6×100-3.6×1
=360-3.6
=356.4
0.25×24
=0.25×4×6
=1×6
=6

解决问题。
某市要建设一条长30km的通信线路,甲队每天建设1.8km,乙队每天建设2.1km。两队合建8天能完成任务吗？

答案： 1.8+2.1=3.9(km)
3.9×8=31.2(km)
31.2＞30
答：两队合建8天能完成任务。