Question

18．用簡便方法計(jì)算

4.8×0.25	2.33×0.5×4	1.2×2.5+0.8×2.5
1.5×105	12.34-4.54+5.46	8.32×2.6+7.3×8.32+0.832

Answer 1

分析 ①先把4.8變成1.2×4，再用乘法結(jié)合律簡算，
②運(yùn)用乘法結(jié)合律可簡算，
③逆用乘法分配律可簡算，
④運(yùn)用乘法分配律可簡算，
⑤可用加法交換律計(jì)算，
⑥先把0.832變成8.32×0.1，再逆用乘法分配律簡算．

解答 解：①4.8×0.25
=（1.2×4）×0.25
=1.2×（4×0.25）
=1.2×1
=1.2

②2.33×0.5×4
=2.33×（0.5×4）
=2.33×2
=4.66

③1.2×2.5+0.8×2.5
=2.5×（1.2+0.8）
=2.5×2
=5

④1.5×105
=1.5×（100+5）
=1.5×100+1.5×5
=150+7.5
=157.5

⑤12.34-4.54+5.46
=12.34+5.46-4.54
=17.8-4.54
=13.26

⑥8.32×2.6+7.3×8.32+0.832
=8.32×2.6+7.3×8.32+8.32×0.1
=8.32×（2.6+7.3+0.1）
=8.32×10
=83.2

點(diǎn)評 此題考查小數(shù)四則混合運(yùn)算順序和靈活運(yùn)用運(yùn)算定律，分析數(shù)據(jù)找到正確的計(jì)算方法．