小學(xué)數(shù)學(xué)競(jìng)賽小數(shù)四則混合運(yùn)算綜合教師版解題技巧培優(yōu)易錯(cuò)難

小學(xué)數(shù)學(xué)競(jìng)賽：小數(shù)四則混雜運(yùn)算綜合.教師版解題技巧培優(yōu)易錯(cuò)難小學(xué)數(shù)學(xué)競(jìng)賽：小數(shù)四則混雜運(yùn)算綜合.教師版解題技巧培優(yōu)易錯(cuò)難/小學(xué)數(shù)學(xué)競(jìng)賽：小數(shù)四則混雜運(yùn)算綜合.教師版解題技巧培優(yōu)易錯(cuò)難小數(shù)四則混雜運(yùn)算綜合授課目的本講主若是經(jīng)過(guò)一些速算技巧，培養(yǎng)學(xué)生的數(shù)感，并經(jīng)過(guò)一些大數(shù)運(yùn)算轉(zhuǎn)變成簡(jiǎn)單運(yùn)算，讓學(xué)生感覺學(xué)習(xí)的成就感，進(jìn)而激發(fā)學(xué)生的學(xué)習(xí)興趣知識(shí)點(diǎn)撥一、運(yùn)算定律⑴加法交換律：abba的等比數(shù)列求和⑵加法結(jié)合律：(ab)ca(bc)⑶乘法交換律：abba⑷乘法結(jié)合律：(ab)ca(bc)⑸乘法分配律：a(bc)abac（反過(guò)來(lái)就是提取公因數(shù)）⑹減法的性質(zhì)：abca(bc)⑺除法的性質(zhì)：a(bc)abc(ab)cacbc(ab)cacbc上面的這些運(yùn)算律，既能夠從左到右順著用，又能夠從右到左逆著用．二、要注意添括號(hào)也許去括號(hào)對(duì)運(yùn)算符號(hào)的影響⑴在“”號(hào)后邊添括號(hào)也許去括號(hào)，括號(hào)內(nèi)的“”、“”號(hào)都不變；⑵在“”號(hào)后邊添括號(hào)也許去括號(hào)，括號(hào)內(nèi)的“”、“”號(hào)都改變，其中“”號(hào)變成“”號(hào)，“”號(hào)變成“”號(hào)；⑶在“”號(hào)后邊添括號(hào)也許去括號(hào)，括號(hào)內(nèi)的“”、“”號(hào)都不變，但此時(shí)括號(hào)內(nèi)不能夠有加減運(yùn)算，只能有乘除運(yùn)算；⑷在“”號(hào)后邊添括號(hào)也許去括號(hào)，括號(hào)內(nèi)的“”、“”號(hào)都改變，其中“”號(hào)變成“”號(hào)，“”號(hào)變成“”號(hào)，但此時(shí)括號(hào)內(nèi)不能夠有加減運(yùn)算，只能有乘除運(yùn)算．例題精講【例1】計(jì)算：200.920.08200.820.07【考點(diǎn)】四則混雜運(yùn)算之提取公因數(shù)【難度】2星【題型】計(jì)算【分析】原式200.920.0820.08200.720.08(200.9200.7)20.080.24.016【答案】4.016【牢固】計(jì)算：20.0931.52.009317200.93.68.【考點(diǎn)】四則混雜運(yùn)算之提取公因數(shù)【難度】2星【題型】計(jì)算【要點(diǎn)詞】學(xué)而思杯，4年級(jí)【分析】原式2.0093152.0093172.0093682.0093153173682.00910002009【答案】2009【牢固】計(jì)算：2.009×43+20.09×2.9+200.9×0.28=.【考點(diǎn)】四則混雜運(yùn)算之提取公因數(shù)【難度】2星【題型】計(jì)算【要點(diǎn)詞】希望杯，6年級(jí)，一試【分析】原式20.094.320.092.920.092.820.09(4.32.92.8)200.9【答案】200.9【牢固】計(jì)算：19993.14199.931.419.99314．【考點(diǎn)】四則混雜運(yùn)算之提取公因數(shù)【難度】2星【題型】計(jì)算【要點(diǎn)詞】第十屆，小數(shù)報(bào)【分析】原式19993.143（20001）9.4218830.58【答案】18830.58【牢固】計(jì)算：199.919.98199.819.97【考點(diǎn)】四則混雜運(yùn)算之提取公因數(shù)【難度】2星【題型】計(jì)算【分析】（法1）原式199.919.9819.98199.719.98(199.9199.7)19.980.23.996（法2）也能夠用湊整法來(lái)解決．原式(2000.1)19.98(2000.2)19.9720019.980.119.9820019.970.219.971.9963.996【答案】3.996【牢固】計(jì)算：10.373.41.719.26.【考點(diǎn)】四則混雜運(yùn)算之提取公因數(shù)【難度】2星【題型】計(jì)算【要點(diǎn)詞】希望杯，5年級(jí)，1試【分析】10.373.41.719.2610.373.43.49.6310.379.633.43.468【答案】68【例2】計(jì)算：6.258.27163.750.8278【考點(diǎn)】四則混雜運(yùn)算之提取公因數(shù)【難度】2星【題型】計(jì)算【分析】原式6.25168.273.750.88.278.27(6.25163.750.8)8.27(1003)8.271008.273851.81【答案】851.81【牢固】計(jì)算：20.0962200.93.972.87．【考點(diǎn)】四則混雜運(yùn)算之提取公因數(shù)【難度】2星【題型】計(jì)算【要點(diǎn)詞】學(xué)而思杯，5年級(jí)，第1題【分析】原式20.096220.093920.0920.096239120.09100

2009【答案】

2009【牢固】計(jì)算：2.89471.531.41.1240.112880.530.1=【考點(diǎn)】四則混雜運(yùn)算之提取公因數(shù)【難度】2星

．【題型】計(jì)算【要點(diǎn)詞】走美杯，5年級(jí)，決賽【分析】原式=2.88×（0.47+0.53）+0.47+1.53+（24-14）×=288+2+1=291【答案】291【牢固】計(jì)算：2237.522.312.523040.72.51＝．【考點(diǎn)】四則混雜運(yùn)算之提取公因數(shù)【難度】2星【題型】計(jì)算【要點(diǎn)詞】走美杯，5年級(jí)，決賽【分析】原式2237.52231.252300.2570.2512238.752230.251223912008【答案】2008【牢固】計(jì)算：19.9837199.82.39.9980【考點(diǎn)】四則混雜運(yùn)算之提取公因數(shù)【難度】2星【題型】計(jì)算【要點(diǎn)詞】第三屆，興趣杯，5年級(jí)【分析】原式19.983719.982319.984019.98（372340）1998【答案】1998【牢固】計(jì)算：3790.000381590.006213.790.121【考點(diǎn)】四則混雜運(yùn)算之提取公因數(shù)【難度】2星【題型】計(jì)算【要點(diǎn)詞】迎春杯，5年級(jí)【分析】原式3.790.0381590.006213.790.1213.79（0.0380.121）0.1596.213.790.1590.1596.210.159（3.796.21）0.159101.59【答案】1.59【牢固】計(jì)算78.161.453.1421.841690.7816【考點(diǎn)】四則混雜運(yùn)算之提取公因數(shù)【難度】2星【題型】計(jì)算【要點(diǎn)詞】希望杯，1試【分析】不難看出式子中7816出現(xiàn)過(guò)兩次：78.16和0.7816，由此能夠聯(lián)想到提取公因數(shù)原式78.161.453.1421.841.6978.1678.16(1.451.69)3.1421.8478.163.143.1421.843.14100314【答案】314【牢固】計(jì)算：7.816×1.45+3.14×2.184+1.69×7.816=_____。【考點(diǎn)】四則混雜運(yùn)算之提取公因數(shù)【難度】2星【題型】計(jì)算【要點(diǎn)詞】希望杯，1試，5年級(jí)【分析】原式=7.816×(1.45+1.69)+3.14×2.184=7.186×3.14+3.14×2.184=31.4【答案】31.4【牢固】計(jì)算：147.758.44.7924092.10.9521479【考點(diǎn)】四則混雜運(yùn)算之提取公因數(shù)【難度】3星【題型】計(jì)算【要點(diǎn)詞】小學(xué)數(shù)學(xué)夏令營(yíng)【分析】原式（147.754409）2.1（0.04790.9521）47910002.14792579【答案】2579【例3】計(jì)算：12.53.6798.33.62星【考點(diǎn)】四則混雜運(yùn)算之提取公因數(shù)【難度】【題型】計(jì)算【分析】原式1253628368336(1252883)365或12.53.6798.312578312528831803.69363653636【答案】5【例4】計(jì)算⑴8.11.381.31.91.311.91.32003200111120037337【考點(diǎn)】四則混雜運(yùn)算之提取公因數(shù)【難度】2星【題型】計(jì)算【分析】⑴原式(8.11.9)1.3(11.98)1.313316⑵原式200320011112003733(373)2003(2001733)1112003222011140060【答案】⑴16⑵40060【例5】計(jì)算：51.28.1119.255370.193【考點(diǎn)】四則混雜運(yùn)算之提取公因數(shù)【難度】星【題型】計(jì)算【分析】稍做辦理，題中數(shù)字就能湊整化簡(jiǎn)，原式51.28.1119.25(51225)0.1951.28.1119.255120.19250.1951.28.151.21.9119.250.251951.210110.251190.25195120.2530996117.5618.5【答案】618.5【例6】計(jì)算：2237.522.312.523040.72.51【考點(diǎn)】四則混雜運(yùn)算之提取公因數(shù)【難度】3星【題型】計(jì)算【要點(diǎn)詞】走美杯，決賽【分析】原式22332.522.352.5232.50.72.50.42.52.5(223322.35230.70.4)2.5(669111.5230.70.4)2.5803.2803.2104803242008【答案】2008【牢固】1.2517.6360.82.6412.5【考點(diǎn)】四則混雜運(yùn)算之提取公因數(shù)【難度】2星【題型】計(jì)算【要點(diǎn)詞】走美杯，初賽，六年級(jí)【分析】1.2517.6360.82.6412.5=1.25(17.626.4)360.8=1.2544360.8=55+45=100【答案】100【例7】計(jì)算：[2007（8.58.51.51.5）10]1600.3．【考點(diǎn)】四則混雜運(yùn)算之提取公因數(shù)【難度】2星【題型】計(jì)算【要點(diǎn)詞】迎春杯【分析】原式[2007（8.51.5）（8.51.5）10]1600.3200771600.320001600.312.50.312.2【答案】12.2【牢固】計(jì)算(98065320)(669864)【考點(diǎn)】四則混雜運(yùn)算之提取公因數(shù)【難度】3星【題型】計(jì)算【分析】注意到在被除數(shù)和除數(shù)的表達(dá)式中均出現(xiàn)了98，而且分別有周邊的數(shù)64與65，我們能夠考慮把被除數(shù)做以下變形：被除數(shù)980(641)32098064(980320)98064660(986466)10所以被除數(shù)是除數(shù)的10倍，所以這道題的答案是10．【答案】10【牢固】⑴2004.051997.052001.051999.05(873477198)(476874199)【考點(diǎn)】四則混雜運(yùn)算之提取公因數(shù)【難度】3星【題型】計(jì)算【分析】(1)原式(3)(1999.052)2001.051999.052001.05＝31999.0522001.05631999.0521999.052261989.05(2)原式(873476873198)(873476476199)＝(873476675)(8734766