2023年五年級數(shù)學上冊五小數(shù)乘法和除法第7課時小數(shù)乘小數(shù)課件蘇教版

,小數(shù)乘小數(shù),第,7,課時,蘇教版 數(shù)學 五年級 上冊,1.自主探索小數(shù)與小數(shù)相乘時位數(shù)不夠的方法，理解其計算方法并能正確計算。,2.培養(yǎng)比較、概括、類比遷移的數(shù)學思維能力，初步的推理和抽象、概括的能力。,3.感受數(shù)學的魅力，增強數(shù)學意識，提高學習數(shù)學的興趣。,3,5,.,2,1,.,5,3,0,7,5,3,7,.,1,.,6,2,.,2,5,0,1,8,4,2,3,0,5,0,4,.,豎式計算。,方法總結：先把小數(shù)乘小數(shù)當作整數(shù)乘法進行計算，再看乘法中有幾位小數(shù)，就從乘得的積右邊起數(shù)出幾位，點上小數(shù)點。,不計算，說出下表各欄的積是幾位小數(shù)。,乘數(shù),0.3,14.2,2.6,0.32,79,1.56,5.58,0.86,乘數(shù),0.5,0.8,0.3,0.87,0.56,0.14,0.9,0.27,積,0.15,11.36,0.78,0.2784,44.24,0.2184,5.022,0.2322,小明在陽臺上擺放了一個花架，它的底面是邊長,0.28,米的正方形。這個花架的占地面積是多少平方米？,分析：,花架底面的形狀是正方形，求花架的面積就是正方形的面積，根據(jù),“,正方形的面積,=,邊長,邊長,”,可以求出。列式為：,0.28,0.28,。,0.28,0.28,（）,0,.,2,8,0,.,2,8,4,2,2,6,5,4,8,7,一共四位小數(shù),四位小數(shù),要從積的右邊起數(shù)出幾位點上小數(shù)點？,位數(shù)不夠怎么辦？,0,這個花架的占地面積是多少平方米？,0.28,0.28,（）,0,.,2,8,0,.,2,8,4,2,2,6,5,4,8,7,位數(shù)不夠用,0,補足,0,.,0.0784,平方米,答：這個花架的占地面積是,0.0784,平方米。,0,.,0,.0,0,0,.,你能給下面各題的積點上小數(shù)點嗎？,1,乘 數(shù),45,45,0.45,0.45,45,0.045,乘 數(shù),16,1.6,1.6,16,0.16,1.6,積,720,72,0.72,7.2,7.2,0.072,根據(jù)第一欄的積，寫出各欄的積。,2,小數(shù)乘小數(shù)的計算方法：,先把小數(shù)乘小數(shù)當作整數(shù)乘法進行計算，再看乘法中有幾位小數(shù)，就從乘得的積右邊起數(shù)出幾位，點上小數(shù)點。,如果積的小數(shù)位數(shù)不夠，就在前面用,0,補足；當乘得的積的末尾有0時，要先點上小數(shù)點，再根據(jù)小數(shù)的性質(zhì)化簡。,乘數(shù),15,1.5,0.15,15,0.015,乘數(shù),48,4.8,4.8,0.48,4.8,積,720,7.2,0.72,7.2,0.072,因為,15,48=720,，,1.5,4.8=7.2,，同理可計算出后面的結果：,0.15,4.8=0.72,；,15,0.4 8=7.2;0.015,4.8=0.072,。,根據(jù)第一欄的積，寫出其他各欄的積。,1,整數(shù)部分沒有要寫,0,占位。,0.015,4.8,的積是幾位小數(shù),?,在哪里點小數(shù)點,?,整數(shù)部分沒有怎么辦,?,因為,15,1000=0.015,，,48,10=4.8,，所以,0.015,4.8,的積等于,720,1000,10=0.072,。,整數(shù)部分沒有要寫,0,占位。,0.85,0.6=0.51,（平方米）,答：長方形鋁板的面積大一些。大,0.02,平方米。,一塊長方形鋁板，長,0.85,米，寬,0.6,米；一塊正方形鋁板，邊長,0.7,米。哪一塊鋁板的面積大一些,?,大多少平方米,?,2,0.7,0.7=0.49,（平方米）,8,5,6,0,1,5,0,1,.,0,.,0,.,5,0,7,7,9,4,0,9,4,.,0,.,0,.,0.51,0.49=0.02,（平方米）,工作效率,時間,=,工作總量,0.5,1.2=0.6,（公頃）,答：,1.2,小時可耕地,0.6,公頃，,0.75,小時可耕地,0.375,公頃。,一臺拖拉機每小時耕地,0.5,公頃，,1.2,小時可耕地多少公頃？,0.75,小時可耕地多少公頃？,3,0.5,0.75=0.375,（公頃）,1,.,2,5,0,6,0,0,6,0,.,7,5,0,.,5,5,7,3,5,7,3,.,0,.,.,0,