五年級(jí)奧數(shù)專題01：小數(shù)的巧算

精品文檔一 小數(shù)的巧算（A） 年級(jí) 班 姓名 得分 一、填空題 1計(jì)算 1.135+3.346+5.557+7.768+9.979=_. 2. 計(jì)算 1.996+19.97+199.8=_. 3. 計(jì)算 9.8+99.8+999.8+9999.8+99999.8=_. 4. 計(jì)算 6.11+9.22+8.33+7.44+5.55+4.56+3.67+2.78+1.89=_. 5. 計(jì)算 1.1+3.3+5.5+7.7+9.9+11.11+13.13+15.15+17.17+19.19=_. 6. 計(jì)算 2.894.68+4.686.11+4.68=_. 7. 計(jì)算 17.4837-17.4819+17.4882=_. 8. 計(jì)算 1.250.322.5=_. 9. 計(jì)算 754.7+15.925=_.10. 計(jì)算 28.6767+32286.7+573.40.05=_. 二、解答題11. 計(jì)算 172.46.2+27240.3812. 計(jì)算 13. 計(jì)算 12.34+23.45+34.56+45.67+56.78+67.89+78.91+89.12+91.23 14. 下面有兩個(gè)小數(shù):, 求a+b,a-b,ab,ab.一 小數(shù)的巧算（B） 年級(jí) 班 姓名 得分 一、真空題 1. 計(jì)算 4.75-9.64+8.25-1.36=_. 2. 計(jì)算 3.17-2.74+4.7+5.29-0.26+6.3=_. 3. 計(jì)算 (5.25+0.125+5.75)8=_. 4. 計(jì)算 34.58.23-34.5+2.7734.5=_.5. 計(jì)算 6.250.16+2640.0625+5.26.25+0.62520=_. 6. 計(jì)算 0.035935+0.035+30.035+0.07610.5=_. 7. 計(jì)算 19.9837-199.81.9+19980.82=_. 8. 計(jì)算 13.59.9+6.510.1=_. 9. 計(jì)算 0.1250.250.564=_.10. 計(jì)算 11.843-8600.09=_.二、解答題11計(jì)算 32.14+64.280.53780.25+0.537864.280.75-864.280.1250.5378.12. 計(jì)算 0.88812573+9993.13. 計(jì)算 1998+199.8+19.98+1.998.14. 下面有兩個(gè)小數(shù): ,試求a+b, a-b, ab, ab.5歡迎下載5歡迎下載。答 案 1. 27.785 2. 221.766原式=(2-0.004)+(20-0.03)+(200-0.2)=222-(0.004+0.03+0.2)=221.766 3. 111109提示:仿上題. 4. 49.55 5. 103.25原式=1.1(1+3+9)+1.01(11+13+19)=1.125+1.0175=103.25 6. 46.8 7. 1748原式=17.4837-17.4819+17.4882=17.48(37-19+82)=17.48100=1748 8. 1原式=(1.250.8)(0.42.5)=11=1 9. 750原式=754.7+5.3(325)=75(4.7+5.3)=7510=750 10. 2867原式=28.6767+3228.67+28.67(200.05)=28.67(67+32+1)=28.67100=2867 11. 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 =2104 12. 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(gè)0,又963+1028=1991,所以0. 0001810.00011=0.0001991 963個(gè)0 1028個(gè)0 1992個(gè)0 13. 9個(gè)加數(shù)中,十位、個(gè)位、十分位、百分位的數(shù)都是19，所以原式=11.11(1+2+9) =11.1145 =499.95 14. a是小數(shù)點(diǎn)后有(1994+3-1=)1996位的小數(shù),b是小數(shù)點(diǎn)后有(1996+2-1=)1997位小數(shù). a+b=0.0001069 a-b=0.0001031 1994個(gè)0 1994個(gè)0 ab=0.0001995 ab=105019= 3990個(gè)0答 案 1. 2 原式=（4.75+8.25）-(9.64+1.36) =13-11 =2 2. 17 原式=(3.71+5.29)+(4.7+6.3)-(2.74+0.26) =9+11-3 =17 3. 89 原式=(5.25+5.75+0.125)8 =(11+0.125)8 =118+0.1258 =88+1 =89 4. 345 原式=34.5(8.23+2.77-1) =34.510 =3455. 62.5原式=6.250.16+2.646.25+5.26.25+6.252 =6.25(0.16+2.64+5.2+2) =6.2510 =62.56. 357. 19988. 199.3 原式=13.5(10-0.1)+6.5(10+0.1) =13.510-13.50.1+6.510+6.50.1 =135-1.35+65+0.65 =(135+65)-(1.35-0.65) =200-0.7 =199.39. 1 原式=0.1250.250.5(842) =(0.1258)(0.254)(0.52) =111 =110. 430 原式=11.843-43200.09 =11.843-431.8 =43(11.8-1.8) =4310 =43011.原式=32.14+64.280.5378(0.25+0.75-80.125) =32.14+64.280.53780 =32.1412. 原式=0.111(8125)73+111(93) =11173+11127 =111(73+27) =111100 =1110013. 原式=(2000-2)+(200-0.2)+(20-0.02)+(2-0.002) =2222-2.222 =2222-(10-7.778) =2222-10+7.778 =2219.778 14. a+b,a的小數(shù)點(diǎn)后面有1998位,b的小數(shù)點(diǎn)后面有2000位,小數(shù)加法要求數(shù)位對(duì)齊,然后按整數(shù)的加法法則計(jì)算,所以 a+b=0.00012508 = 0.00012508 2000位 1996個(gè)0 ,方法與a+b一樣,數(shù)位對(duì)齊,還要注意退位和補(bǔ)零,因?yàn)閍=0.000125，b=0.0008,由12500-8=12492，所以1998位 2000位a-b=0.0012