五年級奧數(shù)題：小數(shù)的巧算(A)

1、精選優(yōu)質(zhì)文檔-傾情為你奉上小數(shù)的巧算（1）教學內(nèi)容：小數(shù)的巧算教學目標：培養(yǎng)學生快速做出小數(shù)計算題的方法與技巧。教學重難點:小數(shù)巧算的計算方法。教學方法：湊整法；交置法；去括號發(fā)。例1.計算 1.135+3.346+5.557+7.768+9.979=_.例2. 計算 1.996+19.97+199.8=_.例3. 計算 9.8+99.8+999.8+9999.8+99999.8=_.例4. 計算 6.11+9.22+8.33+7.44+5.55+4.56+3.67+2.78+1.89=_.例5. 計算 1.1+3.3+5.5+7.7+9.9+11.11+13.13+15.15+17.17+1

2、9.19=_.例6. 計算 2.894.68+4.686.11+4.68=_.例7. 計算 17.4837-17.4819+17.4882=_.例8. 計算 1.250.322.5=_.例9. 計算 754.7+15.925=_.例10. 計算 28.6767+3228.67+573.40.05=_.例11 1.135+3.346+5.557+7.768+9.979=_.例12. 1.996+19.97+199.8=_.例13. 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

3、+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=_.例20. 172.4×6.2+2724×0.381028個0963個0例21.  0.000181×0.

4、00011例22.34+23.45+34.56+45.67+56.78+67.89+78.91+89.12+91.231994個01996個0例23. a= 0.000105 b=0.00019 計算a+b a-b a×b a÷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. 34.5×8.23-34.5+2.77×34.5例28.   6.25×0.16+2

5、64×0.0625+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32.11.8×43-860×0.09例33.32.14+64.28×0.5378×0.25+0.5378&#

6、215;64.28×0.75-8×64.28×0.125×0.5378例34.   0.888×125×73+999×3例35.   1998+199.8+19.98+1.998二、解答題1. 計算 172.46.2+27240.382. 計算 0.0001810.00011 964個0 1029個0 3. 計算 12.34+23.45+34.56+45.67+56.78+67.89+78.91+89.12+91.234. 下面有兩個小數(shù): a=0.000105 b=0.00019 1

7、994個0 1996個0求a+b, a-b, ab, ab.1996個02000個05. a= 0.000125 b=0.0008 求a+b, a-b, ab, ab.1. 27.7852. 221.766原式=(2-0.004)+(20-0.03)+(200-0.2)=222-(0.004+0.03+0.2)=221.7663. 提示:仿上題.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×

8、82=17.48×(37-19+82)=17.48×100=17488. 1原式=(1.250.8)(0.42.5)=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+(1724+1000)0.38=172.46.2+17240.38+10000.38 =172.46.2+172.43.8+380=172.4(6.2+3.8)+380 =172.410+380=1724+380=210412. 181是三位,11是兩位,相乘后18111=1991是四位,三位加兩位是五位,因此1991前面還要添一個0,又963+1028=1991,所以0. 0001810.00011=0.0001991 964個0 1029個0 1993個013. 9個加數(shù)中,十位、個位、十分位、百分位的數(shù)都是19，所以原式=11.11(1+2+9)=11.1145=