To autumn
Teaching objectives
1. Get information from specific situations and find problems.
2. Experience the process of exploring the calculation method of continuous reduction, master the vertical method of continuous reduction through writing, and calculate it accurately.
3. Feel the close relationship between mathematics and life, stimulate interest in learning mathematics, and establish confidence in learning mathematics well.
Important and difficult
Master the calculation method of vertical pen calculation and reduction.
teaching process
First, the scene is presented.
It's fall here. Look, these students have come to Laohutan Ocean Park near their school. They will go to the seaside by boat soon.
(a) Check the map and get information.
Tell me what mathematical information you know from the picture.
Look at the picture for information.
Report: 1. This ship can seat 90 people. There are two teams of students, one with 45 students and the other with 25 students.
(2) Show and solve problems 1.
How many seats are left on the boat after the two teams board? Ask the staff to help you calculate, so that you can know how many tourists you can board. )
Second, the problem study.
1. Read questions and think independently.
2. Group discussion on solving problems can be explained in the exercise book.
3. Student report
Idea 1:
(1) Method analysis: How many empty seats are needed on the ship? You can subtract the number of passengers in two teams in turn, and the formula is 90-45-25.
(2) Explore the calculation method of 90-45-25.
The second student listed the vertical calculation on the blackboard, and the other students tried it in their exercise books.
Unified revision of backdoor exercise:
Health 1:
.
9045
—45 —25
4520
Health 2:
.
90
—45
45
—25
20
Idea 2:
(1) method analysis:
If you want to know how many seats are available on the ship, you can first find out the total number of the two teams, and then subtract the total number of the two teams from the available number, which is how many seats are available on the ship.
45+25=70
90—70=20
Third, comprehensive practice.
1. Show and solve problem 2 (page 4 of the book).
How many people didn't get on the bus when they returned to school?
Teacher's Tip: First, look for known conditions and problems. Then think about solving the problem. Final formula calculation.
2. Fish 18 yuan, carrots 15 yuan, and Aunt Zhang brought 50 yuan. Is that enough?
(1) Say, what mathematical information do you know from the picture?
(2) How much money does Aunt Zhang have left?
3. Smile Belt 100 Yuan Shopping, Story Series 18 yuan, Handmade Series 32 yuan.
(1) What mathematical information did you learn from the shopping receipt?
(2) How much should I get back?
calculate
77-33-2596-39-45 100-9 1-8
Let three children perform on the blackboard, and the others do it independently. Collective proofreading.
The clever dog accidentally stained the statistical table of newspaper subscription.
(page 5 of this book, the statistical table is omitted)
(1) Which stratum subscribes to newspapers the least?
(2) How many children's newspapers did Class Two subscribe to?
How many illustrated books did Class Three subscribe to?
How many illustrated books did Class Four subscribe to? How many short stories are there?
Fourth, class summary, homework.
Exercise the first picture of question 1; Question 3; Question 4.
Design autumn outing with blackboard writing
.
9045 45+25=7090—70=20
—45 —25
4520
.