U3、Protection of the Swan —— three digits multiplied by two digits 三、保护大天鹅——三位数乘两位数 Lesson One 第一课 Protect Man's Good Friend ----- whooper swan 保护人类的好朋友-----大天鹅 Our group of twenty people, an average of four hundred publicity materials per person. 我们一组有20人，平均每人发了400份宣传资料。 There are thirty people in our two groups, with an average of two hundred and ten publicity materials per person. 我们二组有30人，平均每人发了210份宣传资料。 What questions can you ask? 你能提出什么问题? Cooperative exploration 合作探索 How many promotional materials did a group distribute? 一组一共发放了多少份宣传贵料? four hundred multiply twenty(Percentage) 400x 20= (份) Four times two is eight 4x2=8 Four hundred by two eight hundred 400x2-800 Four hundred times twenty equals eight 400x 20=8000 Eight hundred times ten equals eight thousand 800x 10=8000 How many publicity materials did the two groups distribute? 二组一共发放了多少份宣传资料? Two hundred and thirty equals 210x 30= (份) twenty-one times three is sixty-three 21 X 3=63 Two hundred and three equals six hundred and three 210X 3=630 two hundred and twenty one by thirty equals sixty-three 210X 30=6300 Six hundred thirty by ten is six thousand three hundred 630x 10=6300
Lesson two 第二课 twenty-three yuan per bag of millet 谷子每袋23元 Corn twenty-one yuan per bag 玉米每袋21元 Rice twenty-nine yuan per bag 大米每袋29元 In order to help the swan winter, we will buy one hundred and fourteen bags of millet and three hundred and forty bags of rice. 为了帮助大天鹅过冬，我们要买114袋谷子和340袋王米。 What questions can you ask? 你能提出什么问题? Cooperative exploration 合作探索 How much does it cost to buy one hundred and fourteen bags of millet? 买114袋谷子要花多少钱? One hundred and fourteen times twenty-three 114x23=__ (元) How much does it cost to buy three hundred and forty bags of corn? 买340袋玉米要花多少钱? Three hundred forty times twenty equals 340x21= (元) Think about how to calculate three digits multiplied by two digits? 想一想，怎样计算三位数乘两位数? Each bag of feed weighs 46 kg and buys two hundred and fifty bags. With a truck of nine tons, can it be finished at one time? 每袋饲料重46千克，买250袋。 用载重9吨的小货车运，一次能运完吗? The problem can be solved by estimation. Look at forty-six bigger. 解决这个问题用估算就可以。把46看大一些。 forty-six is about fifty 46≈50 Fifty by two hundred and fifty equals twelve thousand five hundred 50x 250=12500(千克) nine tons =nine thousand kg 9吨=9000千克 twelve thousand five hundred kg >nine thousand kg 12500千克>9000千克 So, one time can't be finished. 所以，一次不能运完。 This estimate is not correct. Originally each bag of feed is not so heavy, we estimate to Dali, the result exceeds the actual total amount, therefore makes "can not finish at one time" the judgment is unreasonable. 这样估算不对。 本来每袋饲料没那么重，我们往大里估算，结果超出实际总量，因而作出“一次不能运完”的判断是不合理的。 I estimate that. Look at 46 smaller. 我这样估算。把46看小一些。 forty-six about forty 46≈40 forty by two hundred and fifty equals ten thousand 40x 250=10000(千克) 9 tons =9000 kg 9吨＝9000千克 10000 kg >9000 kg 10000千克>9000千克 So, one time can't be finished. 所以，一次不能运完。 This estimate is correct. Because the quality of each bag of feed is lighter, the estimated results are less than the actual total, so must not be completed. 这样估算对。因为把每袋饲料的质量看轻一些，估算的结果比实际总量少都运不完，所以一定不能运完。 Think about it, how to choose the appropriate evaluation method according to the need to solve practical problems? 想一想，怎样根据解决实际问题的需要，选择合适的估方法呢?
Related links 相关链接 Observe each of the following formulas and tell me what you found. 观察下面每组算式，说说你有什么发现。 Eight times two is sixteen 8x2=16 Eight times twenty equals one hundred sixty 8x 20= 160 Eight times two hundred equals one thousand six hundred 8x 200=1600 Twenty-four times two is forty-eight 24x 2=48 twelve by two in twenty-four 12x 2=24 Six times two is twelve 6x2=12 I find that in the multiplication formula, one factor is invariant, the other factor is multiplied by 10,100, product... 我发现在乘法算式中，一个因数不变，另一个因数分别乘10、100, 积...... I find that one factor is constant and the other factor is divided by... 我发现， 一个因数不变，另一个因数分别除以..... Is this a rule? 这是个规律吗? One factor is invariant, the other factor is multiplied by several, and the product obtained is equal to the original product multiplied by several. One factor is constant, the other factor is divided by several.. 一个因数不变，另一个因数乘几，得到的积就等于原来的积乘几。一个因数不变，另一个因数除以几.... |
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