Question

15．用簡便方法計(jì)算

5.6×3.9-2.6×3.9=	1.8×0.9+0.18=	63÷0.5÷0.2=
12.95×1.1-12.95=	1.2×9.9=	9.43×1.01=
2.55×1.5+1.5+6.45×1.5=	5.5÷4+4.5×0.25=

Answer 1

分析 ①根據(jù)乘法分配律，計(jì)算得解；
②0.18=1.8×0.1，然后根據(jù)乘法分配律，計(jì)算得解；
③根據(jù)除法的性質(zhì)，計(jì)算得解；
④根據(jù)乘法分配律，計(jì)算得解；
⑤9.9=10-0.1，然后根據(jù)乘法分配律，計(jì)算得解；
⑥1.01=1+0.01，然后根據(jù)乘法分配律，計(jì)算得解；
⑦根據(jù)乘法分配律，提取1.5，計(jì)算得解；
⑧除以4等于乘0.25，然后根據(jù)乘法分配律，計(jì)算得解．

解答 解：①5.6×3.9-2.6×3.9
=（5.6-2.6）×3.9
=3×3.9
=11.7

②1.8×0.9+0.18
=1.8×0.9+1.8×0.1
=1.8×（0.9+0.1）
=1.8×1
=1.8

③63÷0.5÷0.2
=63÷（0.5×0.2）
=63÷0.1
=630

④12.95×1.1-12.95
=12.95×（1.1-1）
=12.95×0.1
=1.295

⑤1.2×9.9
=1.2×（10-0.1）
=1.2×10-1.2×0.1
=12-0.12
=11.88

⑥9.43×1.01
=9.43×（1+0.01）
=9.43×1+9.43×0.01
=9.43+0.0943
=9.5243

⑦2.55×1.5+1.5+6.45×1.5
=（2.55+1+6.45）×1.5
=10×1.5
=15

⑧5.5÷4+4.5×0.25
=5.5×0.25+4.5×0.25
=（5.5+4.5）×0.25
=10×0.25
=2.5

點(diǎn)評 考查了運(yùn)算定律與簡便運(yùn)算，四則混合運(yùn)算．注意運(yùn)算順序和運(yùn)算法則，靈活運(yùn)用所學(xué)的運(yùn)算律簡便計(jì)算．