人教版小學(xué)數(shù)學(xué)五年級下冊第五單元分?jǐn)?shù)加減混合運算第一課時

1、課題： 分?jǐn)?shù)加減混合運算(一) 教學(xué)目標(biāo)1、通過教學(xué)，使學(xué)生掌握分?jǐn)?shù)加減混合運算的順序和計算方法，并掌握帶有小括號的分?jǐn)?shù)加減混合運算的順序及算法。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)成用簡明、靈活的方法解決問題的習(xí)慣。重點難點掌握分?jǐn)?shù)加減混合運算的順序和計算方法。 教學(xué)過程 第一課時一、復(fù)習(xí)導(dǎo)入1 說一說下列各題的運算順序。112+8-13 16-4+21 24-(18+3) 2 . 老師指出：分?jǐn)?shù)加減混合運算的運算順序和整數(shù)加減混合運算的運算順序相同。設(shè)計意圖這一環(huán)節(jié)，通過形象生動的課件，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)問題？生：喬木林比灌木叢多幾分之幾？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）老師出示一個問題：“森林部分比草地部分多幾分之幾？" (4）提問：森林部分指什么？怎樣列式？(5）請學(xué)生試著算一算，集體交流計算方法。技術(shù)官員村位于位于亞運城東部，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)計算方法：計算分?jǐn)?shù)加減混合運算時，可以分步通分也可以一次通分進行計算。計算時，可以根據(jù)題目的特點和自己的情況靈活選擇方法。設(shè)計意圖 讓學(xué)生體會到把異分母分?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。再者通過學(xué)生自己對兩種方法的比較，靈活選擇簡便的計算方法。2 出示例1 的第二個問題：“裸露地面儲存的地下水

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：在這個問題中，把什么看作單位“1 " ？是什么意思？ ( 2 ）請學(xué)生列出算式：1 或1 ( ) ( 3 ）請學(xué)生試著計算，并指名板演這兩種方法的計算過程。1 1 ( ) = =1 ( ) = =1 = 提問：比較這兩種方法有什么不同？帶有小括號的分?jǐn)?shù)加減混合運算該怎樣計算？3 小結(jié)。提問：你能說一說分?jǐn)?shù)加減混合運算的順序嗎？引導(dǎo)學(xué)生歸納概括出：分?jǐn)?shù)加減混合運算與整數(shù)加減混合運算的順序相同，也是按照從左往右的順序計算，帶有小括號的先算小括號里面的，再算小括號外面的。 設(shè)計意圖：這一環(huán)節(jié)，在學(xué)生原有知識經(jīng)驗的基礎(chǔ)上，放手

17、讓學(xué)生自己去探索分?jǐn)?shù)加減混合運算的方法，鼓勵學(xué)生相互交流，然后全班交流，進而探討分?jǐn)?shù)加減混合運算的計算順序。三、鞏固練習(xí)、深化提高。1 完成教材第118頁的“做一做。學(xué)生試著獨立完成，集體交流計算過程，重點看運算順序及書寫美觀情況。2 完成教材第120 頁練習(xí)二十三的第1 4 題。學(xué)生獨立完成，集體訂正。第2 4 題，鼓勵學(xué)生用不同的方法解答。3某市舉辦一次數(shù)學(xué)競賽，設(shè)一、二、三等獎若干名。獲一、二等獎的占獲獎總?cè)藬?shù)的，獲二、三等獎的占獲獎總?cè)藬?shù)的。獲二等獎的占獲獎總?cè)藬?shù)的幾分之幾？設(shè)計意圖讓學(xué)生小組分工合作提出問題、解決問題，親身體驗合作學(xué)習(xí)的快樂和成功的喜悅。在鞏固應(yīng)用中進一步掌握分?jǐn)?shù)加減

18、混合運算的計算順序，提高計算的準(zhǔn)確率和速度。四、梳理知識，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)對你有什么幫助或啟示？3、你這節(jié)課的表現(xiàn)如何？你覺得還有哪些的同學(xué)表現(xiàn)比較棒？ 設(shè)計意圖這一環(huán)節(jié)的設(shè)計，起到提綱挈領(lǐng)的作用。先對學(xué)生本堂課的表現(xiàn)給予了肯定和表揚，以增強學(xué)生學(xué)好數(shù)學(xué)的信心。接著，讓學(xué)生用自己的語言說說學(xué)到了什么本領(lǐng)，既讓學(xué)生鞏固了所學(xué)知識，又培養(yǎng)了學(xué)生的綜合、概括能力。最后，讓學(xué)生提醒大家計算時還應(yīng)該注意什么，一方面給優(yōu)等生提供了展示的機會，另一方面也讓全班學(xué)生對本堂課所學(xué)的重點、難點和容易發(fā)生錯誤之處得以回顧和反思，有利于知識的掌握、理解和深化。五、課堂檢測課堂檢測a一、 填空1、0.63里面有63個（）分之一，化成分?jǐn)?shù)是。2、把0.7、0.25、這六個數(shù)按從大到小的順序排列。3、把5克鹽放進45克水里，鹽占鹽水的。二、計算下列各題，（6分）（）三、解決問題1、一個加工廠，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b一、解方程。（8分）x=1 x= 4x0.8x=6.4 5x5×11195二、列式計算（或列方程）。（5分）（1）從1