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请把下面的数字简便计算,还要解说,

来源:学生作业帮 编辑:拍题作业网作业帮 分类:数学作业 时间:2024/04/28 23:26:10
请把下面的数字简便计算,还要解说,
(1)0.9+9.9+99.9+999.9+9999.9 (2)24.78-(4.78-0.89) (3)12.5×16-0.56×99-0.56 (4)4/5÷75%+1/5×4/3 (5)5.75÷8+12.5%×2.25
(1)0.9+9.9+99.9+999.9+9999.9
=1-0.1+10-0.1+100-0.1+1000-0.1+10000-0.1
=(10000+1000+100+10+1)-0.5
=11110.5
(2)24.78-(4.78-0.89)
=24.78-4.78+0.89
=20+0.89
=20.89
(3)12.5×16-0.56×99-0.56
=12.5×8×2-0.56×(99+1)
=100×2-0.56×100
=200-56
=144
(4)4/5÷75%+1/5×4/3
=4/5×4/3 +1/5×4/3
=(4/5 +1/5)×4/3
=1×4/3
=4/3
(5)5.75÷8+12.5%×2.25
=5.75×1/8+2.25×1/8
=(5.75+2.25)×1/8
=8×1/8
=1