《圓的周長》說課稿（北師大版）

1、圓的周長說課稿（北師大版）一、說教材圓的周長選自北師大版小學數(shù)學六年級上冊“圓”的第三節(jié)。本課教學是以長方形、正方形周長知識為認知基礎的，是對前面所學“圓的認識”的深化，也是后面學習圓的面積等知識的基礎。本課起著承前啟后的作用，是小學幾何初步知識教學中的一項重要內(nèi)容。根據(jù)課程標準和教材編寫意圖，確立本節(jié)教學目標如下：1.知識目標：知道什么是圓的周長；理解圓周率的意義；理解掌握圓的周長的計算公式。2.能力目標：會初步運用公式解決生活中一些簡單的實際問題。3.思想目標：通過祖沖之與圓周率故事的介紹，激發(fā)學生作為中華兒女的自豪感。教學重點：探究并發(fā)現(xiàn)圓的周長與直徑的關系。教學難點：運用圓的周長知識解

2、決一些簡單的實際問題。二、說教法、學法根據(jù)教學內(nèi)容和學生的認識規(guī)律，我首先采取課件演示的方法幫助學生認識圓的周長，滲透轉化思想；然后利用實驗法引導學生認識、理解圓周率，并推導出圓周長的計算公式，培養(yǎng)學生操作技能，提高學生分析、比較、推理、概括的能力；最后運用自學輔導法，引導學生自己去思考、測量、計算，最終發(fā)現(xiàn)圓的周長與它的直徑和半徑的關系，從而學生提高自學水平。在教學中，注重學生的獨立思考及小組交流，交互運用各種學習形式，達到發(fā)展智力，培養(yǎng)能力的教學目標。教學準備：多媒體課件。每個學生都準備三個大小不同的、直徑為整數(shù)的圓片，一根線條，一把直尺。三、說教學過程（一）創(chuàng)設情境，激情導入課件出示阿凡

3、提的小黑驢與國王的小花驢賽跑的故事。引導學生觀察并思考：要求小花驢所走路程，實際是求圓的什么？讓學生揭示課題：圓的周長。（應用多媒體課件輔助教學，能有效地激發(fā)學生的學習興趣，使學生產(chǎn)生強烈的學習欲望，從而形成良好的學習動機。）（二）自主合作，探究新知教具演示，直觀感知，結合認知認識圓的周長。（學生獨立實驗，用繞線法、滾動法量出圓的周長，教師指導操作要點，培養(yǎng)學生的動手實踐能力。）2.小組合作，完成實驗。a.量一量、記一記：學生測量圓的周長、圓的直徑，然后記下數(shù)據(jù)，培養(yǎng)學生的實踐操作能力。b.比一比：比較數(shù)據(jù)，揭示關系。學生繼續(xù)實驗并算出每個圓周長除以它的直徑的商，把商記錄下來。通過計算學生發(fā)現(xiàn)

4、：這三個圓中，每個圓的周長，都是它的直徑長度的3倍多一些。得出結論：所測量的其他圓的周長也是它的直徑的3倍多一些。（在實驗操作過程中培養(yǎng)學生動手操作的技能、技巧，提高學生分析、比較、推理、概括的能力。）3.介紹圓周率。先介紹表示這個3倍多一些的數(shù)，是一個固定不變的數(shù)，我們稱它為圓周率。用式子表示：圓的周長直徑=圓周率（）介紹的讀寫方法。最后結合畫像介紹古代數(shù)學家祖沖之與圓周率的故事，激發(fā)學生作為中華兒女的自豪感。同時指出：圓周率是一個無限小數(shù)，小學階段取它的近似值為3.14。學生總結歸納出圓的周長計算公式：圓的周長=圓的直徑圓周率，用字母表示為c=d。課件顯示直徑50米的圓形跑道和它的外接正方

5、形跑道示意圖。請學生觀察思考圓的直徑和正方形的邊長是多少，然后利用公式快速算一算，這兩個跑道的周長是多少？看看國王和阿凡提的比賽到底是不是公平。4.課件出示：已知圓形草地的半徑25米，計算圓形草地的周長。引發(fā)學生思考，得出用半徑求周長的公式：c=2r。（應用多媒體課件教學能使課堂信息量加大，使學生易于接受所學知識，并主動參與教學，在愉快的氣氛、交互討論中掌握了教學的重點、難點，教學效果非常好。）5.實踐應用。阿凡提看到自家的圓形驢欄有點松動了，就決定用些粗鐵絲把驢柵欄圍上3圈加固一下。阿凡提想請你們幫忙，計算這個半徑是4米的柵欄需用多長的鐵絲？學生快速計算并交流：先求出圓的周長，也就是圍一周需

6、多少鐵絲，然后再乘以3,就求出圍3圈共需用多少鐵絲。（通過柵欄圍鐵絲的實例體現(xiàn)進行圓周長計算公式的實踐應用價值。）（三）強化訓練，形成能力課件出示必做題、選做題、拓展題。必做題（找學困生匯報）：1.選擇填空a.車輪滾動一周，前進的距離是求車輪的（）a.半徑b.直徑c.周長b.圓的周長是直徑的（）倍。a. 3.14 b. c.3c.大圓的周長除以直徑的商（ ）小圓的周長除以直徑的商。a.大于b.小于 c.等于2.求下面各圓的周長d=8dm;r=5cm;d=6m; r=3dm。選做題（找中等生匯報）：（1）汽車車輪的半徑為0.3米，它滾動1圈前進多少米？滾動1000圈前進多少米？（2）花壇的周長是

7、62.8米，你能求出這個圓形花壇的直徑嗎？拓展題（找優(yōu)等生匯報）：從一張邊長為6厘米的正方形紙上剪下一個最大的圓，這個圓的周長是多少厘米？（課件出示必做題、選做題、拓展題，針對性強，效果好：必做題有利于學困生消化所學知識，使之學有所得；選做題有利于學困生和中等生的提高：拓展題有利于優(yōu)等生思維的拓展，使每個學生都能得到發(fā)展和提高。）（四）總結提高，指導實踐學生匯報本節(jié)課的收獲。（引導學生回顧、總結本節(jié)所學知識、學習方法及獲得的情感體驗。）四、點評這節(jié)課，教師通過數(shù)學教學與多媒體課件的有效整合，使課堂信息量加大，教學過程圖文并茂、生動活潑。在教學中，教師起組織、引導作用，根據(jù)學生實際情況進行有針對

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