Question

19．脫式計算（帶*號的要簡算）
19.8×0.54÷0.081
*29×10.1              
1.89+8.11×2.5
*0.25×201-0.25
*8.7×0.99
*0.87×6.6+0.87×3.4．

Answer 1

分析 ①先算乘法再算除法．
②④⑤⑥都用乘法分配律計算，（a+b）×c=a×c+b×c．
③先算乘法再算加法．

解答 解：①19.8×0.54÷0.081
=10.692÷0.081
=132

②29×10.1
=29×（10+0.1）
=29×10+29×0.1
=290+2.9
-292.9

③1.89+8.11×2.5
=1.89+20.275
=22.165

④0.25×201-0.25
=0.25×（201-1）
=0.25×200
=50

⑤8.7×0.99
=8.7×（1-0.01）
=8.7×1-8.7×0.01
=8.7-0.087
=8.613

⑥0.87×6.6+0.87×3.4
=0.87×（6.6+3.4）
=0.87×10
=8.7

點評 此題考查了學生對小數(shù)四則混合運算題的計算能力，以及用乘法分配律靈活巧算的能力．