北師大版四年級下冊《文具店》課件1

1、北師大版四年級數(shù)學(xué)下冊北師大版四年級數(shù)學(xué)下冊本節(jié)課我們主要來學(xué)習(xí)小數(shù)乘本節(jié)課我們主要來學(xué)習(xí)小數(shù)乘法，同學(xué)們通過對整數(shù)乘法的法，同學(xué)們通過對整數(shù)乘法的復(fù)習(xí)來探索小數(shù)乘法的計算方復(fù)習(xí)來探索小數(shù)乘法的計算方法，能夠達到獨立解決有關(guān)小法，能夠達到獨立解決有關(guān)小數(shù)乘法的實際問題的水平。數(shù)乘法的實際問題的水平。2.2.一支圓珠筆一支圓珠筆 2 2 元，買元，買 4 4 支要多少錢？支要多少錢？2 2 4 = 4 = 2 + 2+ 2 + 2 =2 + 2+ 2 + 2 = 1.oral calculation 25254 =4 = 12 12 5 =5 = 7 7 20 =20 = 2.5 +2 =2.5

2、 +2 = 3003002 =2 = 2 2角角4 =4 = 3.6 -2.4 =3.6 -2.4 = 4.7 +2.6 =4.7 +2.6 = 5 1.8 =5 1.8 = What information do you know from the ichnography? Can you ask some maths questions? 買買 4 4 塊橡皮需要多少元？塊橡皮需要多少元？Do you know how to estimate it?買買 4 4 塊橡皮需要多少元？塊橡皮需要多少元？方法二方法二：方法三：方法三：需要需要0.80.8元元方法一：方法一：求幾個相同加數(shù)和的簡便

3、運算求幾個相同加數(shù)和的簡便運算.0.3 30.90.80.4 2算一算：算一算：0.70.71 =1 = 0.1 0.1 5 =5 = 0.40.46 =6 = 0.30.35 =5 = 0.020.024 =4 = 0.080.087 =7 = 0.70.70.50.52.42.41.51.50.080.080.560.5640.3 = 0.3 4你能計算你能計算4 40.30.3嗎？與同學(xué)交流你的想法。嗎？與同學(xué)交流你的想法。交換兩個因數(shù)的位置交換兩個因數(shù)的位置,積不變。積不變。0.10.5110比一比，誰最快比一比，誰最快0.80.83 =3 = 7 70.5 =0.5 = 1.41.4

4、2 =2 = 0.70.710=10= 0.060.065 =5 = 4 40.09 =0.09 = 0.010.0115 =15 = 2.1 2.1 4 =4 = 2.42.43.53.52.82.87 70.30.30.360.360.150.158.48.4How do we multiply a decimal by a whole number?we should look at the decimal as a whole number.1.每千克蘋果每千克蘋果3.2元，媽媽買了元，媽媽買了3千克，千克，一共要用多少元？一共要用多少元？解決問題：解決問題：2.小明每小時走小明每小時走 5千米，千米， 1.5可以走多少千米？可以走多少千