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1、三位數(shù)乘兩位數(shù)的筆算,三位數(shù)乘兩位數(shù)的筆算,西師大版四年級(jí)數(shù)學(xué)上冊(cè),教學(xué)目標(biāo),本節(jié)課我們主要來(lái)學(xué)習(xí)三位數(shù)乘以兩位數(shù)的筆算,同學(xué)們要結(jié)合兩位數(shù)乘以兩位數(shù)筆算的方法,正確的列豎式計(jì)算三位數(shù)乘以兩位數(shù)的計(jì)算題,在計(jì)算的過(guò)程中注意因數(shù)中有零的情況。,(1)3盒的枝數(shù):,2 4,3,,,2,7,,,1,(2)10盒的枝數(shù):,2 4,1 0,,,0,4,,,2,(3)13盒的枝數(shù):,7 2,2 4 0,,,2,1,3,2 4,1 3,,,2,7,0,4,2,,2,1,3,,243的積,,2410的積(個(gè)位的不寫(xiě)),,,做完下面各題,2 3,1 3,,,9,6,3,2,,9,9,2,做一做,,1 2,4 2
2、,,,4,2,8,4,,4,0,5,1 3,2 4,,,2,5,6,2,,2,1,3,212 34 =,2 1 2,3 4,,,8,4,8,,2124的積,6,3,6,,21230的積,,8,0,2,7,2,做完下面各題,3 2 1,1 3,,,3,6,9,1,2,3,,3,7,1,4,做一做,,1 3 2,3 2,,,4,6,2,6,9,3,,4,2,2,4,2 1 4,2 3,,,2,4,6,8,2,4,,2,2,9,4,一個(gè)因數(shù)是兩位數(shù)的乘法法則,1先用兩位數(shù)個(gè)位上的數(shù)去乘另一個(gè)因數(shù), 得數(shù)的末位和兩位數(shù)的個(gè)位對(duì)齊;,再用兩位數(shù)十位上的數(shù)去乘另一個(gè)因數(shù), 得數(shù)的末位和兩位數(shù)的十位對(duì)齊;,
3、然后把兩次乘得的數(shù)加起來(lái),48 72 ,4 8,7 2,,,6,9,,6,5,4,3,7,7,7,28, 8,56,+ 5, 33,7,4, 28,8,4,我國(guó)發(fā)射的第一顆人造地球衛(wèi)星,繞地球一周 要用114分繞地球59周要用多少分?,1 1 4,5 9,,,1 0 2 6,0,,6,2,7,6,114 59___________(分),7,5,4,6 8,3 6,,,8,0,4,4,0,2,,8,4,4,2,做一做,,1 7 6,4 7,,,2,3,2,4,0,7,,2,7,2,8,3 0 9,2 5,,,5,4,5,8,1,6,,5,2,7,7,1,1,360 24 =,3 6 0,2 4
4、,,,0,4,,0,4,6,8,8 6 4 0,2,7,4,1,0,3 6 0,2 4,,,4,,0,4,6,8,2,7,4,1,簡(jiǎn)便 算法:,,265 30 =,2 6 5,3 0,,,0,0,,0,5,9,7,9,7,0,5,2 6 5,3 0,,,5,0,9,7,,做一做,,35024,8400,3 5 0,2 4,,,0,4,,0,0,4,8,7,1,0,7360,4380,7 3,6 0,,,8,3,0,4,18650,9300,1 8 6,5 0,,,0,3,0,9,計(jì)算450 20 ,4 5 0,2 0,,,0,0,0,9,,想一想:怎樣算比較簡(jiǎn)便?,做一做,,23040,9200,15060,9000,1,2下面的計(jì)算方法對(duì)嗎?你有什么看法?,因數(shù)末尾有0的簡(jiǎn)便算法:,因數(shù)末尾有0的乘法,可以先把0前面的數(shù)相乘, 然后看兩個(gè)因數(shù)的末尾一共有幾個(gè)0,就在乘得的 數(shù)的末尾添寫(xiě)幾個(gè)0。,本課小結(jié),本節(jié)課我們主要學(xué)習(xí)了三位數(shù)乘以兩位數(shù)的乘法的筆算,同學(xué)們要能夠列豎式計(jì)算三位數(shù)乘以兩位數(shù)的乘法,并且能夠解決實(shí)際的問(wèn)題。,