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1、三年级数学和差问题三年级数学和差问题上海福山外国上海福山外国上海福山外国上海福山外国语语小学小学小学小学Shanghai Fushan Foreign Language Primary SchoolShanghai Fushan Foreign Language Primary SchoolShanghai Fushan Foreign Language Primary SchoolShanghai Fushan Foreign Language Primary School上海福山外国上海福山外国上海福山外国上海福山外国语语小学小学小学小学Shanghai Fushan Foreign La
2、nguage Primary SchoolShanghai Fushan Foreign Language Primary SchoolShanghai Fushan Foreign Language Primary SchoolShanghai Fushan Foreign Language Primary School上海福山外国上海福山外国上海福山外国上海福山外国语语小学小学小学小学Shanghai Fushan Foreign Language Primary SchoolShanghai Fushan Foreign Language Primary SchoolShanghai F
3、ushan Foreign Language Primary SchoolShanghai Fushan Foreign Language Primary School例1 菜场运来白菜和萝卜共70筐，白菜比萝卜多18筐，运来白菜和萝卜各有多少筐？让我们让我们画线段图画线段图表表示已知条件和问题。示已知条件和问题。萝卜白菜共70筐白菜比萝卜多18筐解:70-18=52(筐)52 2=26(筐)-萝卜 26+18=44(筐)-白菜 或70-26=44(筐)-白菜答:运来萝卜26筐.运来白菜44筐.上海福山外国上海福山外国上海福山外国上海福山外国语语小学小学小学小学Shanghai Fushan
4、Foreign Language Primary SchoolShanghai Fushan Foreign Language Primary SchoolShanghai Fushan Foreign Language Primary SchoolShanghai Fushan Foreign Language Primary School【练一练】1.1.五五1 1班共有班共有6464人，其中男生比女生多人，其中男生比女生多4 4人。人。五五1 1班男、女生各有多少人？班男、女生各有多少人？64-4=60(人)60 2=30(人)-女生 30+4=34(人)-男生上海福山外国上海福山外国上
5、海福山外国上海福山外国语语小学小学小学小学Shanghai Fushan Foreign Language Primary SchoolShanghai Fushan Foreign Language Primary SchoolShanghai Fushan Foreign Language Primary SchoolShanghai Fushan Foreign Language Primary School2.2.南浦大桥和杨浦大桥共长南浦大桥和杨浦大桥共长34683468米，米，杨浦大桥比南浦大桥长杨浦大桥比南浦大桥长1414米，米，两座大桥各长多少米？两座大桥各长多少米？【练一练】
6、3468-14=3454(米)3454 2=1727(米)-南浦大桥 1727+14=1741(米)-杨浦大桥上海福山外国上海福山外国上海福山外国上海福山外国语语小学小学小学小学Shanghai Fushan Foreign Language Primary SchoolShanghai Fushan Foreign Language Primary SchoolShanghai Fushan Foreign Language Primary SchoolShanghai Fushan Foreign Language Primary School【例例2】甲、乙两仓库共存粮甲、乙两仓库共存粮
7、600包，包，如果从甲仓运如果从甲仓运50包到乙仓，包到乙仓，则两仓库存粮数相等，则两仓库存粮数相等，问甲、乙两仓库各存粮多少包？问甲、乙两仓库各存粮多少包？600-100=500(包)500 2=250(包)-乙仓库 250+100=350(包)-甲仓库甲运50包给乙就一样多了，说明甲乙相差100包上海福山外国上海福山外国上海福山外国上海福山外国语语小学小学小学小学Shanghai Fushan Foreign Language Primary SchoolShanghai Fushan Foreign Language Primary SchoolShanghai Fushan Forei
8、gn Language Primary SchoolShanghai Fushan Foreign Language Primary School3.3.小英和小勇共为学校图书馆补图书小英和小勇共为学校图书馆补图书9696本，本，如果小英给小勇如果小英给小勇7 7本，本，那么两人补图书的本书就一样多，那么两人补图书的本书就一样多，原来小英和小勇补图书各多少本？原来小英和小勇补图书各多少本？【练一练】96-14=82(本)82 2=41(本)-小勇 41+14=55(本)-小英上海福山外国上海福山外国上海福山外国上海福山外国语语小学小学小学小学Shanghai Fushan Foreign La
9、nguage Primary SchoolShanghai Fushan Foreign Language Primary SchoolShanghai Fushan Foreign Language Primary SchoolShanghai Fushan Foreign Language Primary School4.4.小红和小明平均收集小红和小明平均收集3636张邮票张邮票,小明比小红多小明比小红多1212张张,他们分别有几张他们分别有几张?【练一练】362-12=60(本)60 2=30(本)-小红 30+12=42(本)-小明上海福山外国上海福山外国上海福山外国上海福山外国语语
10、小学小学小学小学Shanghai Fushan Foreign Language Primary SchoolShanghai Fushan Foreign Language Primary SchoolShanghai Fushan Foreign Language Primary SchoolShanghai Fushan Foreign Language Primary School 思思 维维 操操 场场 1.相邻两个奇数之和是相邻两个奇数之和是100，这两个数分别是多少？，这两个数分别是多少？100-2=98(本)98 2=49 49+2=51上海福山外国上海福山外国上海福山外国上海
11、福山外国语语小学小学小学小学Shanghai Fushan Foreign Language Primary SchoolShanghai Fushan Foreign Language Primary SchoolShanghai Fushan Foreign Language Primary SchoolShanghai Fushan Foreign Language Primary School2.2.两箱水果共两箱水果共100100千克，千克，如果从第一箱中取出如果从第一箱中取出1010千克放到第二箱里，千克放到第二箱里，这时两箱水果一样重。这时两箱水果一样重。这两箱水果原来各有多少千
12、克？这两箱水果原来各有多少千克？思思 维维 操操 场场 100-20=80(千克)80 2=40(千克)-第二箱 40+20=60(千克)-第一箱上海福山外国上海福山外国上海福山外国上海福山外国语语小学小学小学小学Shanghai Fushan Foreign Language Primary SchoolShanghai Fushan Foreign Language Primary SchoolShanghai Fushan Foreign Language Primary SchoolShanghai Fushan Foreign Language Primary School3.3.三
13、三(1)(1)班和三班和三(2)(2)班共有班共有9494人。人。如果从三如果从三(1)(1)班调班调2 2人到三人到三(2)(2)班，班，两个班级的人数就同样多了。两个班级的人数就同样多了。两个班级原来各有多少学生？两个班级原来各有多少学生？思思 维维 操操 场场 94-4=90(人)90 2=45(人)-三（2）45+4=49(人)-三(1)上海福山外国上海福山外国上海福山外国上海福山外国语语小学小学小学小学Shanghai Fushan Foreign Language Primary SchoolShanghai Fushan Foreign Language Primary Scho
14、olShanghai Fushan Foreign Language Primary SchoolShanghai Fushan Foreign Language Primary School4.4.三（三（1 1）班和三（）班和三（2 2）班平均每班种树）班平均每班种树215215棵，棵，已知三（已知三（1 1）比三（）比三（2 2）班多种）班多种8282棵，棵，求三（求三（1 1）班、三（）班、三（2 2）班各种多少棵树？）班各种多少棵树？思思 维维 操操 场场 2152-82-=348(棵)3482=174(棵)-三（2）174+82=256(棵)-三（1）上海福山外国上海福山外国上海福
15、山外国上海福山外国语语小学小学小学小学Shanghai Fushan Foreign Language Primary SchoolShanghai Fushan Foreign Language Primary SchoolShanghai Fushan Foreign Language Primary SchoolShanghai Fushan Foreign Language Primary School5.学校买了学校买了2 2套课桌椅共花了套课桌椅共花了106106元，元，已知每张课桌比每张课椅贵已知每张课桌比每张课椅贵1717元，元，课桌和课椅的单价各是多少元？课桌和课椅的单价各是多少元？思思 维维 操操 场场 1062-17=36(元)362=18(元)-椅子 18+17=35(元)-课桌上海福山外国上海福山外国上海福山外国上海福山外国语语小学小学小学小学Shanghai Fushan Foreign Language Primary SchoolShanghai Fushan Foreign Language Primary SchoolShanghai Fushan Foreign Language Primary SchoolShanghai Fushan Foreign Language Primary School结束结束