五年级奥数题：小数的巧算(A)

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1、小数的巧算（1）教学内容：小数的巧算教学目标：培养学生快速做出小数计算题的方法与技巧。教学重难点:小数巧算的计算方法。教学方法：凑整法；交置法；去括号发。例1.计算1.135+3.346+5.557+7.768+9.979=_____.例2.计算1.996+19.97+199.8=_____.例3.计算9.8+99.8+999.8+9999.8+99999.8=_____.例4.计算6.11+9.22+8.33+7.44+5.55+4.56+3.67+2.78+1.89=_____.例5.计算1.1+3.3+5.5+7.7+9

2、.9+11.11+13.13+15.15+17.17+19.19=_____.例6.计算2.894.68+4.686.11+4.68=_____.例7.计算17.4837-17.4819+17.4882=_____.例8.计算1.250.322.5=_____.例9.计算754.7+15.925=_____.例10.计算28.6767+3228.67+573.40.05=_____.5例11．1.135+3.346+5.557+7.768+9.979=_____.例12.1.996+19.97+199.8=_____.例13.

3、6.11+9.22+8.33+7.44+5.55+4.56+3.67+2.78+1.89=_____.例14.1.1+3.3+5.5+7.7+9.9+11.11+13.13+15.15+17.17+19.19=_____例15.2.89×4.68+4.68×6.11+4.68=_____.例16.17.48×37-17.48×19+17.48×82=_____.例17.1.25×0.32×2.5=_____.例18.75×4.7+15.9×25=_____.例19.28.67×67+32×286.7+573.4×0.05=__

4、___.例20.172.4×6.2+2724×0.381028个0963个0例21. 0.00．．．0181×0.00．．．0115例22.34+23.45+34.56+45.67+56.78+67.89+78.91+89.12+91.231994个01996个0例23. a=0.00．．．0105b=0.00．．．019计算a+ba-ba×ba÷b例24.  4.75-9.64+8.25-1.36例25.3.71-2.74+4.7+5.29-0.26+6.3例26.(5.25+0.125+5.75)×8例27.34.5×8.

5、23-34.5+2.77×34.5例28.  6.25×0.16+264×0.0625+5.2×6.25+0.625×20例28.0.035×935+0.035+3×0.035+0.07×61×0.5例29.19.98×37-199.8×1.9+1998×0.82例30.13.5×9.9+6.5+5.75×10.1例31.0.125×0.25×0.5×64例32.11.8×43-860×0.095例33.32.14+64.28×0.5378×0.25+0.5378×64.28×0.75-8×64.28×0.125×0.5378

6、例34.  0.888×125×73+999×3例35.  1998+199.8+19.98+1.998二、解答题1.计算172.46.2+27240.382.计算0.00…01810.00…011964个01029个03.计算12.34+23.45+34.56+45.67+56.78+67.89+78.91+89.12+91.234.下面有两个小数:a=0.00…0105b=0.00…0191994个01996个0求a+b,a-b,ab,ab.1996个02000个05. a=0.00．．．0125b=0.00．．．08求a

7、+b,a-b,ab,ab.51.27.7852.221.766原式=(2-0.004)+(20-0.03)+(200-0.2)=222-(0.004+0.03+0.2)=221.7663.111109提示:仿上题.4.49.555.103.25原式=1.1(1+3+…+9)+1.01(11+13+…+19)=1.125+1.0175=103.256.46.87.1748原式=17.48×37-17.48×19+17.48×82=17.48×(37-19+82)=17.48×100=17488.1原式=(1.250.8)(0.4

8、2.5)=11=19.750原式=754.7+5.3(325)=75(4.7+5.3)=7510=75010.2867原式=28.6767+3228.67+28.67(200.05)=28.67(67+32+1)=28.67100=286711.原式=172.46.2+(17