This lesson is the first lesson of Unit 6 "Addition and subtraction within 100". The calculation method of integer decimal addition and subtraction is basically the same as that within 10, but the counting unit is different. Here, the counting unit is ten. For example, 10+20, when calculating, it is thought that 1 ten plus twenty is three tens, which is 30. This arrangement helps students to deepen their understanding that numbers in the same unit can be added or subtracted directly. It is the basis for learning to add and subtract any two numbers in the future.
Second, the analysis of learning situation
Students have mastered the reading, writing and composition of numbers within 100 before learning integer decimal addition and subtraction; Integer ten plus one digit and corresponding subtraction; Master the mixed operation of addition and subtraction and addition and subtraction. Therefore, it is not difficult to learn this part.
Third, the teaching objectives
1, by creating problem situations, let students apply their knowledge of the composition of numbers and master the calculation method of integer decimal addition and subtraction.
2. Students explore the process of integer decimal addition and subtraction through independent exploration and cooperative communication. Feel the way of thinking in mathematics.
3. Cultivate students' cooperative ability to feel life mathematics, experience rich emotional experience, and stimulate students' interest in learning mathematics.
Fourthly, the importance and difficulty of teaching.
1, key point: master the calculation method of integer decimal addition and subtraction.
2. Difficulties: Understand the calculation method of integer decimal addition and subtraction.
Teaching methods of verbs (abbreviation of verb)
Intuitive demonstration method and independent inquiry method
Sixth, the teaching process.
(1) Create situations and introduce new knowledge.
Teacher: Students, today the teacher will take you to a mysterious place to play. (Showing courseware) Yes, it is the kingdom of mathematics, magical and beautiful, and there are many interesting mathematical knowledge. However, in order to enter the mathematical kingdom, we must first find the golden key to open the mathematical kingdom.
Show the courseware for review:
1, oral calculation:
4+5= 30+5= 7-5= 6+3= 28-8=
9-7= 8-6= 20+6= 45-5=? 56-50=
2. Fill in the blanks:
(1)50 has (? ) ten.
(2) Eight tens are (? )。
(3) A number is 6 and a number is 0. This number (? )。
Teacher: What are the similarities between the numbers 50, 80 and 60?
Health: It's all 0.
Conclusion: You are really an observant boy. We call a two-digit number with a unit of 0 an integer ten. Today we will go to the mathematics kingdom to learn the addition and subtraction of integer decimal. (Write "Add and subtract whole ten" on the blackboard) Students read the questions together.
Second, teacher-student interaction, exploring new knowledge
Teacher: The students have found the golden key to the kingdom of mathematics. Look, the door to the kingdom of mathematics is open. (The teacher said while demonstrating the courseware) Let's see what interesting things have happened in the mathematics kingdom!
1, integer ten plus integer ten
Teacher: The children in the mathematics kingdom are going to learn new courses, and the teacher is giving them new books!
Look at this photo carefully. What mathematical information have you collected?
Student Report: There are 10 books on the left and 20 books on the right.
Teacher: Look at these books. What math questions can you ask?
Students ask questions independently: How many books are there?
Teacher: Your question is really great! How to solve this problem?
Students speak and teachers write on the blackboard: 10+20 =
Teacher: How to calculate? Please discuss in groups of four.
Classroom communication:
(1) Count:10,20,30
(2) Add the numbers on the same digit: 1+2=3, 10+20=30.
(3) Composition of numbers: 1 Ten and two tens together form three tens, which is 30.
Teacher: It's amazing that the students have come up with so many methods! So, did we get the right result? Please verify it with a stick.
The students put up sticks and called their classmates to demonstrate.
2. Subtract the whole ten from the whole ten
Teacher: If the teacher takes 20 of these 30 books, what math questions can you ask?
Health: How many copies are left?
Students write down their own solutions on the exercise paper, and call the students to report the calculation method.
Students quickly put a stick to verify whether the calculation result is correct.
Third, consolidate the practice.
1, say it
Teacher:/kloc-what is all ten within 0/00? Please choose two integers in the same table and say an addition formula and a subtraction formula.
Step 2 do the math
( 1)3+2= ? (2)? 4+5= ? (3)6-4= ? (4)7-3=
30+20= ? 40+50= ? 60-40= 70-30=
Teacher: What do you find by comparing the two formulas in each group?
3. Look at the chart.
Teacher: There are some such pencils in the stationery store of Math Kingdom. Take a closer look at this picture, don't you think?
Here we are. What? How many formulas can you list?
Name the students and work out the formula. Communicate with the class.
Step 4 solve the problem
(1) How much does it cost to buy the above three things?
(2) How much should I get back after paying the salesman 100 yuan?
Students answer independently, and the whole class communicates.
Teacher: What other math questions can you ask to test your little friend?
Students ask questions and assign other students to answer them.
Four. abstract
What did you gain from this class?
Students speak, others add.
Teacher: Look, how amazing mathematics is! As long as you are diligent in thinking, you will certainly find more magical knowledge. Today we learned the calculation method of integer decimal addition and subtraction in the mathematics kingdom. Please think about a question after class.
Verb (abbreviation for verb) assignment
Fill in 10, 20, 30, 40, 50 in the box below, so that the sum of three numbers on each straight line is equal.