苏教版二年级数学下册知识点

苏教版二年级数学下册知识点

苏教版二年级数学下册知识点

第一单元：有余数的除法

有余数除法的意义是在平均分物体时，有时会有剩余，这种除法就是有余数的除法。在有余数的除法中，余数一定比除数小。除法列竖式计算方法是先写除号，被除数写在除号里，除数写在除号外面左侧，商写在除号的外面，被除数上面，并与被除数个位对齐。然后将除数和商的积写在被除数的下面，相同的数位要对齐。最后将被除数减去商和除数的乘积，得到的结果写在横线下面，与个位对齐。有余数除法的试商方法是先想想被除数里面最多有几个除数，再利用乘法口诀试商。在除法算式中，各部分之间的关系是被除数除以除数等于商加余数，被除数等于商乘以除数加余数，被除数等于除数乘以商加余数，余数等于被除数减去商乘以除数。

第二单元：时分秒

认识钟面是时分秒的基础。钟面上最短最粗的针是时针，较短较粗的是分针，最细最长的是秒针。钟面上有12个大格，每个大格里有5个小格。钟面上共有60个小格。时针走1大格是1小时，时针走1大格分针走1圈，也就是60小格，1时等于60分。分针走1小格是1分，走1大格是5分。秒针走1小格是1秒，走1大格是5秒。分针走1小格，秒针走1圈，1分等于60秒。认识整时方法是分针指着12，时针指着几就是几时。时针、分针、秒针全部重合的时间是12时，时针和分针成一条直线的时间是6时，时针和分针成直角的时间是3时和9时。认识几时几分方法是时针指在两个数之间，算小数，时针指在12和1之间，算12时，分针指着几，表示几个5分钟。记录时间有两种方法，一种是文字法，如5时50分；另一种是用电子表法，几时就写几，再写“：”，后面写分时要占两位，分针不够整十的，十位要用占位，如8时零5分写作8：05.认识大约几时方法是时针接近几就是几时，此时，分针一般指在数字12左右。计算两段时间之间的时间方法是用结束的时间减去开始的时间，整时减整时，分钟减分钟，分钟不够减向整时借1时，在分钟上加60分钟再减。整时借出的1时要记得减去。 Comparison of Time: When the units are different。they

should be converted into the same unit before comparison。In a

race (or doing something)。the more time it takes to cover the

same distance (or do the same thing)。the slower the speed (or

lower the efficiency)。the less time it takes。the faster the speed

(or higher the efficiency).

Unit Three: Recognizing ns

Mathematics Knowledge Point 2 of Grade 2.Book 2 of Su n

3

1.Recognizing the four ns of east。south。west。and north

1) In the morning。facing the sun。the front is east。the

back is west。the left is north。and the right is south.

2) The method of XXX: facing south and back north。left is

east and right is west。facing north and back south。left is west

and right is east。facing east and back west。left is north and right

is south。facing west and back east。left is south and right is

north. 2.ns on the map: The map is usually drawn according to the

rule of "north is up。south is down。west is left。and east is

right."

3.Method of drawing a simple schematic diagram: First。choose an n point and draw it at the center of the plane diagram。Then determine the n of each object relative to the n point。and

draw it on the paper according to the rule of "north is up。south is

down。west is left。and east is right." Use the symbol "↑" to XXX.

4.Method of reading a simple route map to describe the

walking route:

1) Look at the route map to determine your own n。and take

your own n as the center.

2) Determine the n of the target and surrounding objects

according to the rule of "north is up。south is down。west is left。and east is right."

3) Determine the walking route based on the n of the target

and the distance。(Generally。take the n of the object after the

word "in" as the center。and take the n of the object before the

word "of" as the center.) 5.Recognizing the four ns of northeast。southeast。XXX。XXX: Starting from "east"。XXX called northeast。and the n een

east and south is called southeast。starting from "west"。XXX。and the XXX.

pass:

The red pointer points to the north。and the white pointer

points to the south.

Tree rings: XXX point to the south。and the dense ones point

to the north.

XXX: XXX point to the north。and the dense ones point to

the south.

Clear night: XXX XXX.

n of the shadow: opposite to the n of the sun.

Unit Four: Recognizing XXX

1.Digit order:

1) Starting from the right。the first digit is the unit digit。the

second digit is the tens digit。the third digit is the hundreds digit。XXX。and the XXX. 2) The。een any two adjacent digits is ten: 10 ones make

10.10 tens make 100.10 hundreds make 1000.and 10 thousands

make .

3) The smallest three-digit number is 100.and the largest

three-digit number is 999.the smallest four-digit number is

1000.and the largest four-digit number is 9999.

2.Reading and writing numbers XXX:

1) When writing numbers。start from the highest digit。and

write the number in each digit according to the digit order。If

there is no number in a digit。write a placeholder in that digit。Use Arabic numerals 1.2.3.to write numbers.

1、读万以内的数：读数时，从高位到低位，每个数字用汉字读出来，中间只有一个或连续两个零时，只读一个零，末尾的零不读。例如：3421读作“三千四百二十一”，9000读作“九千”，读作“七万”。

2、认识算盘上的数字：在算盘上，每个珠子代表一定的数值，下珠代表1，上珠代表5.通过拨动珠子，可以进行加减运算。

3、比较数字的大小：当两个数字的位数不同时，位数多的数字大；当两个数字的位数相同时，从最高位开始比较，最高位大的数字大，如果最高位相同，则比较下一位，以此类推，直到比较出大小为止。

4、近似数：当一个数接近几百或几千时，可以用几百或几千来近似表示。如果一个数的十位小于5，则直接写百位上的数字；如果十位大于等于5，则把百位上的数字加1.同样，如果一个数的百位小于5，则直接写千位上的数字；如果百位大于等于5，则把千位上的数字加1.近似数用约等于符号“≈”表示。

5、数字的组合：可以把数字从大到小或从小到大排列组合，以得到最大或最小的数。但是，如果有0，不能把0排在最高位。

6、长度单位：长度单位从大到小依次为米、分米、厘米、毫米。相邻的两个单位之间进率为10.

7、长度单位换算：不同的长度单位之间可以通过换算进行转换，例如1米=10分米、1分米=10厘米、1厘米=10毫米。

8、长度单位的加减和比较：当对不同的长度单位进行加减或比较大小时，必须先将它们换算成相同的单位。

9、测量长度：在测量物体长度时，需要选择合适的长度单位。比较长的物体可以用米做单位，而比较短的物体则可以根据实际情况和显示的数字选择合适的长度单位。