Basic knowledge of mathematics in People's Education Press: addition and subtraction within 100 1, integer ten plus integer ten, what is the sum of the numbers on ten, and the sum is ten. Subtract the whole ten from the whole ten, subtract the number on the tenth place from the remaining few, and the difference is dozens.
2. Two digits plus one digit. First, add the single digit of two digits and that single digit to get a few digits as a sum, and the ten digits of the sum are the numbers on the ten digits of two digits. Two digits are added to the integer. First, the number on the two-digit number and the number on the integer are added together as the ten digits of the sum, and the single digit of the sum is the number on the single digit of the two-digit number. Calculate two numbers plus a number or an integer of ten, or calculate by combining numbers.
3. Three algorithms for adding one digit to two digits and adding more than ten digits: (1) Add the digits of two digits to get a new two digits, and then add this new two digits to the ten digits of the original two digits. (2) First round the two digits to an integer of ten, and then add the remainder. (3) First round a number to an integer of ten, and then add the remainder. Such as: 25+7=? ( 1)5+7= 12,20+ 12=32; (2)25+5=30,30+2=32; (3)7+3= 10,22+ 10=32。
4. Subtract one digit from two digits. If one digit is enough, just use it to subtract one digit. The difference is the number in one digit, and the number in the tenth digit is the number in the original two digits. When subtracting two digits from an integer, first subtract the integer from the ten digits of the two digits, and then add the ten digits to the single digits of the original two digits.
5, compare the size, the general formula should be calculated and then compared.
6. If two digits subtract one digit, and one digit is not enough, there are two algorithms: (1) divide the minuend into ten digits and ten digits, subtract one digit from the ten digits first, and then add the difference with the ten digits. (2) Divide the minuend into a new two-digit sum 10, first subtract one digit from ten, and then add the difference with the new two digits. No matter which algorithm, the ten digits of the calculation result are less than the original 1.
7. Subtract a number from an integer, then divide the minuend into tens and 10, and add the difference after subtracting a number from 10 to tens.
8. In the mixed formula of addition and subtraction or addition and subtraction several times, it is generally calculated from left to right. If there are brackets, they must be counted in brackets first. The function of parentheses is to change the order of operations (that is, what is counted first, then what is counted).
9. To find the sum of several identical numbers, you can use the method of continuous addition; To find out how many numbers a number contains, we can use the method of continuous subtraction.
10. To solve this practical problem, you can add, subtract, count, circle and column.
1 1, two digits plus one digit, if the digits add up to ten, the number on the tenth digit should be more than the original 1, and how many 1 remain after the digits add up to ten?
Basic knowledge of mathematics in People's Education Press: the properties such as finding the law 1, color, quantity, size, shape, numerical relationship and direction are called laws. The core of some laws is repetition, while others are development. A group of objects can be arranged regularly if they are arranged repeatedly in turn (at least twice).
2. When looking for patterns, first observe the arrangement of figures, and then observe the arrangement of numbers.
3. The arrangement rule of numbers can be that the last number is more or less than the previous number, that is, the rule can be found by calculating the difference between two adjacent numbers; It can be the third number obtained by adding the first two numbers; It can be a repeated arrangement of a set of numbers.
4, the arrangement of graphics, graphics color, quantity, size, shape, direction, overlap, etc. Repetition or development are laws. Repeated rules must be circled in groups before finding irregular or the next figure. If it is the law of development, it is easy to find mistakes or speculate on the unknown.
5. Identifying plane figures can be distinguished by the characteristics of edges. No matter what classification you give, you must first think about the classification criteria.
Basic knowledge of mathematics in People's Education Press: Know the number within 100; 1; 10 is ten; 10 is one hundred. Ten is a number consisting of ten and one. For example, 75 is a number of seven tens and five ones, and the number of five tens and seven ones is 57.
From the right, the first place is one, the second place is ten, and the third place is one hundred. The same number means different things with different numbers. One digit means several ones, ten digits means dozens and hundreds. Reading and writing should start from the high position, that is, from the first position on the left. The reading is expressed in Chinese characters, such as: 98; The written numbers are represented by Arabic numerals, such as 98. When writing numbers, if there is nothing in the numbers, you should use 0 to occupy the position.
3. Only one number is called a number; Ten digits are composed of numbers, no matter how many digits each number has, it is called two digits; If there are numbers on the hundred digits, it is called three digits, such as 100. How much in a unit means how many 1, how many 10 in a tenth and how many 100 in a hundredth.
4, compare the size of the number, the number of two digits is greater than the number of ten digits; Ten digits are the same, with more digits; Two digits must be greater than one digit.
5. According to the numerical order from front to back, the number at the back is greater than the number at the front.
4. Describe the size between two numbers. More? 、? Less? 、? Much more? 、? Much less? 、? Closer? Describe it later.
5. When solving the problem that a number has several other numbers, we can use a circle, a number or a combination of numbers to solve it.
6. A few dozen plus several is several tens, for example: 50+4=54, 80+6 = 86; A few plus dozens equals dozens, such as: 8+50=58, 7+60=67. In other words, add a few digits, and the ten digits are written as before.
7. Decrement of several tens is equal to several tens, such as: 95-5=90, 73-3=70, that is, ten digits are copied, and the unit is 0; Minus dozens equals several, such as: 63-60=3, 48-40=8, that is, ten digits are 0 and one digit is the minuend.