【解答】解:(1)6.28+3.5+3.72
=6.28+3.72+3.5
=10+3.5
=13.5
(2)2.5×3.2×125
=2.5×(4×0.8)×125
=(2.5×4)×(0.8×125)
=10×100
=1000
(3)÷9+×
=×+×
=(+)×
=×
=
(4)1000÷12.5÷8
=1000÷(12.5×8)
=1000÷100
=10
(5)2.5÷×
=4×
=7
(6)÷[﹣(1﹣)]
=÷[﹣]
=÷
=
【点评】考查了运算定律与简便运算,四则混合运算.注意运算顺序和运算法则,灵活运用所学的运算定律进行简便计算.
3.【分析】(1)先计算左边,依据等式的性质,方程两边同时除以1.2求解;
(2)方程的两边同时加上2x,然后方程的两边同时减去2,再同时除以2求解;
(3)根据比例的基本性质,变成 0.2x=0.75×16,然后等式的两边同时除以0.2求解.
【解答】解:(1)x+20%x=
1.2x=0.4
1.2x÷1.2=0.4÷1.2
x=
(2)36﹣2x=12
36﹣2x+2x=12+2x
12+2x﹣12=36﹣12
2x÷2=24÷2
x=12
(3)=
0.2x=0.75×16