P5 1 case 1, case 2, class activities 1, 2, 3.

Teaching objectives:

1, you can calculate the subtraction of vertical three digits.

2. Be able to experience the diversity of calculation methods in combination with calculation, and communicate their own methods and processes with classmates.

3, combined with learning activities, cultivate the spirit of independent thinking, active exploration and the consciousness of active cooperation with classmates.

Teaching difficulties:

If the number of digits is not enough, it should be reduced from ten digits 1 do 10.

Teaching aid preparation:

Physical diagram, counter, etc.

Teaching process:

First, review.

Oral calculation:

13-8 ? 28-9 ? 30-5 ? 42-20 ? 35+5 ? 35+50 ? 74-23

450+400 ? 450-400 ? 70-30 ? 420-20 ? 350+500 ? 880-800 ? 880-80

Second, create shopping situations and explore new knowledge.

I. Learning examples 1

1, Teacher: Show me a calculator and let the students say what it is. Now the teacher has 340 yuan money on him. I want to buy a 120 calculator. Ask the children to help the teacher figure out how much money is left.

2. Students calculate independently and then tell your deskmate how you do it.

3. Say the answer and write it on the blackboard.

The first type: 300- 100=200, 40-20=20, 200+20=220.

The second type: vertical calculation.

The third type: 340-120 = 340-100-20 = 240-20 = 220;

The fourth type: 340-120 = 340-20-100 = 320-100 = 220;

Second, study example 2.

1. Students look at the table in Example 2 and tell the meaning of the question: There are 876 students in avant-garde primary school, including 438 girls and how many boys?

2. After giving birth to the independent formula, first estimate how many boys there are, and then calculate how many boys there are.

3. The teacher called the roll on the board:

4. Observe these two examples and think about what should be paid attention to in calculation.

(1) The same number is aligned;

(2) Decrease from the unit, if the unit is not reduced enough, then decrease from the tenth time 1 to 10.

Third, classroom activities:

1, P52- 1, fill in the blanks with pictures.

Ask the students to look at the picture and say the meaning of the question, and then fill it in the book directly.

2. In question P52-2, students look at the table and guide them to understand the meaning of the word "phase difference".

(That is, how many words written by Li Hong are more than those written by Wang Feng? Or how many words did Wang Feng write less than Li Hong? Then the students calculate independently in the exercise book.

3.P52-3。 By comparison, whose home is near the school? How close is it?

Look at the picture independently and then calculate it in the form of a column chart.

Fourth, the class summary:

What did you learn in this class? What have you learned?