Question

4．脫式計(jì)算，能簡(jiǎn)算的要簡(jiǎn)算
2.55×7.1+2.45×7.1
194-64.8÷1.8×0.9
0.64×25×7.8+2.2
0.75×102．

Answer 1

分析 （1）根據(jù)乘法分配律簡(jiǎn)算即可．
（2）首先計(jì)算除法和乘法，然后計(jì)算減法即可．
（3）首先把0.64分成0.8×0.8，然后根據(jù)乘法交換律和乘法結(jié)合律簡(jiǎn)算即可．
（4）首先把102分成100+2，然后根據(jù)乘法分配律計(jì)算即可．

解答 解：（1）2.55×7.1+2.45×7.1
=（2.55+2.45）×7.1
=5×7.1
=35.5

（2）194-64.8÷1.8×0.9
=194-36×0.9
=194-32.4
=161.6

（3）0.64×25×7.8+2.2
=0.8×0.8×25×7.8+2.2
=（0.8×25）×（0.8×7.8）+2.2
=20×6.24+2.2
=124.8+2.2
=127

（4）0.75×102
=0.75×（100+2）
=0.75×100+0.75×2
=75+1.5
=76.5

點(diǎn)評(píng) 此題主要考查了運(yùn)算定律與簡(jiǎn)便運(yùn)算，要熟練掌握，注意乘法運(yùn)算定律的應(yīng)用．