人教版小學(xué)數(shù)學(xué)五年級(jí)下冊(cè)第五單元分?jǐn)?shù)加減混合運(yùn)算第一課時(shí)

1、課題： 分?jǐn)?shù)加減混合運(yùn)算(一) 教學(xué)目標(biāo)1、通過(guò)教學(xué)，使學(xué)生掌握分?jǐn)?shù)加減混合運(yùn)算的順序和計(jì)算方法，并掌握帶有小括號(hào)的分?jǐn)?shù)加減混合運(yùn)算的順序及算法。2、培養(yǎng)學(xué)生遷移、類推的能力和歸納、概括的能力。3、養(yǎng)成用簡(jiǎn)明、靈活的方法解決問(wèn)題的習(xí)慣。重點(diǎn)難點(diǎn)掌握分?jǐn)?shù)加減混合運(yùn)算的順序和計(jì)算方法。 教學(xué)過(guò)程 第一課時(shí)一、復(fù)習(xí)導(dǎo)入1 說(shuō)一說(shuō)下列各題的運(yùn)算順序。112+8-13 16-4+21 24-(18+3) 2 . 老師指出：分?jǐn)?shù)加減混合運(yùn)算的運(yùn)算順序和整數(shù)加減混合運(yùn)算的運(yùn)算順序相同。設(shè)計(jì)意圖這一環(huán)節(jié)，通過(guò)形象生動(dòng)的課件，激發(fā)學(xué)生的學(xué)習(xí)興趣，不僅溫習(xí)了舊知，而且也為學(xué)生學(xué)習(xí)新知架起了橋梁。真正起到了承上啟下

2、的作用二、探究新知1 出示例1 的表格。地貌類型占公園面積的幾分之幾喬木林灌木叢草地(1)從表格中你能得到哪些數(shù)學(xué)信息？表中各分?jǐn)?shù)表示什么意思？(2）你能提出那些數(shù)學(xué)問(wèn)題？生：?jiǎn)棠玖直裙嗄緟捕鄮追种畮?？喬木林比草地多幾分之幾？喬木林、灌木叢和草地共占公園面積的幾分之幾？(3）老師出示一個(gè)問(wèn)題：“森林部分比草地部分多幾分之幾？" (4）提問(wèn)：森林部分指什么？怎樣列式？(5）請(qǐng)學(xué)生試著算一算，集體交流計(jì)算方法。技術(shù)官員村位于位于亞運(yùn)城東部，主干道二以東石樓涌以西的地塊，占地面積、m2，總建筑面積、m2，共包括地下室南區(qū)、地下室北區(qū)、地上部分1棟12棟、服務(wù)中心、室外工程等多個(gè)單體工程。其

3、中住宅面積m2，共12棟，17棟建筑層數(shù)為11層，812棟11層（局部復(fù)式頂層），首層局部架空，布置公建配套設(shè)施。integrated energy, chemicals and textile yibin city, are the three core pillars of the industry. in 2014, the wuliangye brand value to 73.58 billion yuan, the city's liquor industry slip to stabilise. promoting deep development of integrat

4、ed energy, advanced equipment manufacturing industry, changning district, shale gas production capacity reached 277 million cubic metres, built the country's first independent high-yield wells and pipelines in the first section, the lead in factory production and supply to the population. 2.1-3

5、gdp growth figure 2.1-4 yibin, yibin city, yibin city, fiscal revenue growth 2.1.4 topography terrain overall is southwest, north-eastern state. low mountains and hills in the city landscape as the main ridge-and-valley, pingba small fragmented nature picture for "water and the second land of t

6、he seven hills". 236 meters to 2000 meters above sea level in the city, low mountain, 46.6% hills 45.3%, pingba only 8.1%. 2.1.5 development of yibin landscapes and distinctive feature in the center of the city, with limitations, and spatial structure of typical zonal group, 2012-cities in buil

7、ding with an area of about 76.2km2. from city-building situation, "old town-the south bank" center construction is lagging behind, disintegration of the old city is slow, optimization and upgrading, quality public service resources are still heavily concentrated in the old town together. s

8、outhbank centre has not been formed, functions of the service area space is missing. meanwhile, peripheral group centres service was weak and inadequate accounting for city development, "suspicious" pattern could not be formed. as regards transport, with the outward expansion of cities, ci

9、ties have been expanding, centripetal city traffic organization has not changed, integrated energy, chemicals and textile yibin city, are the three core pillars of the industry. in 2014, the wuliangye brand value to 73.58 billion yuan, the city's liquor industry slip to stabilise. promoting deep

10、 development of integrated energy, advanced equipment manufacturing industry, changning district, shale gas production capacity reached 277 million cubic metres, built the country's first independent high-yield wells and pipelines in the first section, the lead in factory production and supply t

11、o the population. 2.1-3 gdp growth figure 2.1-4 yibin, yibin city, yibin city, fiscal revenue growth 2.1.4 topography terrain overall is southwest, north-eastern state. low mountains and hills in the city landscape as the main ridge-and-valley, pingba small fragmented nature picture for "water

12、and the second land of the seven hills". 236 meters to 2000 meters above sea level in the city, low mountain, 46.6% hills 45.3%, pingba only 8.1%. 2.1.5 development of yibin landscapes and distinctive feature in the center of the city, with limitations, and spatial structure of typical zonal gr

13、oup, 2012-cities in building with an area of about 76.2km2. from city-building situation, "old town-the south bank" center construction is lagging behind, disintegration of the old city is slow, optimization and upgrading, quality public service resources are still heavily concentrated in

14、the old town together. southbank centre has not been formed, functions of the service area space is missing. meanwhile, peripheral group centres service was weak and inadequate accounting for city development, "suspicious" pattern could not be formed. as regards transport, with the outward

15、 expansion of cities, cities have been expanding, centripetal city traffic organization has not changed,方法（一） +-=+-=-=-=方法（二）+-= +-= -= ( 5 ）小結(jié)計(jì)算方法：計(jì)算分?jǐn)?shù)加減混合運(yùn)算時(shí)，可以分步通分也可以一次通分進(jìn)行計(jì)算。計(jì)算時(shí)，可以根據(jù)題目的特點(diǎn)和自己的情況靈活選擇方法。設(shè)計(jì)意圖 讓學(xué)生體會(huì)到把異分母分?jǐn)?shù)化成同分母分?jǐn)?shù)的必要，即只有相同單位才能直接相加。再者通過(guò)學(xué)生自己對(duì)兩種方法的比較，靈活選擇簡(jiǎn)便的計(jì)算方法。2 出示例1 的第二個(gè)問(wèn)題：“裸露地面儲(chǔ)存的地下水

16、占降水量的幾分之幾？( l ）先讓學(xué)生看懂表格內(nèi)容，然后老師提問(wèn)：在這個(gè)問(wèn)題中，把什么看作單位“1 " ？是什么意思？ ( 2 ）請(qǐng)學(xué)生列出算式：1 或1 ( ) ( 3 ）請(qǐng)學(xué)生試著計(jì)算，并指名板演這兩種方法的計(jì)算過(guò)程。1 1 ( ) = =1 ( ) = =1 = 提問(wèn)：比較這兩種方法有什么不同？帶有小括號(hào)的分?jǐn)?shù)加減混合運(yùn)算該怎樣計(jì)算？3 小結(jié)。提問(wèn)：你能說(shuō)一說(shuō)分?jǐn)?shù)加減混合運(yùn)算的順序嗎？引導(dǎo)學(xué)生歸納概括出：分?jǐn)?shù)加減混合運(yùn)算與整數(shù)加減混合運(yùn)算的順序相同，也是按照從左往右的順序計(jì)算，帶有小括號(hào)的先算小括號(hào)里面的，再算小括號(hào)外面的。 設(shè)計(jì)意圖：這一環(huán)節(jié)，在學(xué)生原有知識(shí)經(jīng)驗(yàn)的基礎(chǔ)上，放手

17、讓學(xué)生自己去探索分?jǐn)?shù)加減混合運(yùn)算的方法，鼓勵(lì)學(xué)生相互交流，然后全班交流，進(jìn)而探討分?jǐn)?shù)加減混合運(yùn)算的計(jì)算順序。三、鞏固練習(xí)、深化提高。1 完成教材第118頁(yè)的“做一做。學(xué)生試著獨(dú)立完成，集體交流計(jì)算過(guò)程，重點(diǎn)看運(yùn)算順序及書(shū)寫(xiě)美觀情況。2 完成教材第120 頁(yè)練習(xí)二十三的第1 4 題。學(xué)生獨(dú)立完成，集體訂正。第2 4 題，鼓勵(lì)學(xué)生用不同的方法解答。3某市舉辦一次數(shù)學(xué)競(jìng)賽，設(shè)一、二、三等獎(jiǎng)若干名。獲一、二等獎(jiǎng)的占獲獎(jiǎng)總?cè)藬?shù)的，獲二、三等獎(jiǎng)的占獲獎(jiǎng)總?cè)藬?shù)的。獲二等獎(jiǎng)的占獲獎(jiǎng)總?cè)藬?shù)的幾分之幾？設(shè)計(jì)意圖讓學(xué)生小組分工合作提出問(wèn)題、解決問(wèn)題，親身體驗(yàn)合作學(xué)習(xí)的快樂(lè)和成功的喜悅。在鞏固應(yīng)用中進(jìn)一步掌握分?jǐn)?shù)加減

18、混合運(yùn)算的計(jì)算順序，提高計(jì)算的準(zhǔn)確率和速度。四、梳理知識(shí)，總結(jié)升華1、這節(jié)課的學(xué)習(xí)你有什么收獲？2、本節(jié)課的學(xué)習(xí)對(duì)你有什么幫助或啟示？3、你這節(jié)課的表現(xiàn)如何？你覺(jué)得還有哪些的同學(xué)表現(xiàn)比較棒？ 設(shè)計(jì)意圖這一環(huán)節(jié)的設(shè)計(jì)，起到提綱挈領(lǐng)的作用。先對(duì)學(xué)生本堂課的表現(xiàn)給予了肯定和表?yè)P(yáng)，以增強(qiáng)學(xué)生學(xué)好數(shù)學(xué)的信心。接著，讓學(xué)生用自己的語(yǔ)言說(shuō)說(shuō)學(xué)到了什么本領(lǐng)，既讓學(xué)生鞏固了所學(xué)知識(shí)，又培養(yǎng)了學(xué)生的綜合、概括能力。最后，讓學(xué)生提醒大家計(jì)算時(shí)還應(yīng)該注意什么，一方面給優(yōu)等生提供了展示的機(jī)會(huì)，另一方面也讓全班學(xué)生對(duì)本堂課所學(xué)的重點(diǎn)、難點(diǎn)和容易發(fā)生錯(cuò)誤之處得以回顧和反思，有利于知識(shí)的掌握、理解和深化。五、課堂檢測(cè)課堂檢測(cè)a一、 填空1、0.63里面有63個(gè)（）分之一，化成分?jǐn)?shù)是。2、把0.7、0.25、這六個(gè)數(shù)按從大到小的順序排列。3、把5克鹽放進(jìn)45克水里，鹽占鹽水的。二、計(jì)算下列各題，（6分）（）三、解決問(wèn)題1、一個(gè)加工廠，第一天加工飼料噸，比第二天少加工噸，兩天一共加工多少噸飼料？2、一塊地的面積約公頃，其中的種玫瑰花，種郁金香，其余的部分種杜鵑花，種杜鵑花占總面積的幾分之幾？ 課堂檢測(cè)b一、解方程。（8分）x=1 x= 4x0.8x=6.4 5x5×11195二、列式計(jì)算（或列方程）。（5分）（1）從1