Teaching content: P9: Example 4 "Doing"

Teaching objectives:

Knowledge and skills: Through learning, students can understand the operation sequence of elementary arithmetic with brackets.

Process and method: familiar with the practice of operation.

Emotion, attitude and values: cultivate students' good study habits.

Teaching emphasis: Understand the operation order of elementary arithmetic with brackets.

Teaching difficulty: the necessity of understanding brackets.

Teaching aid: multimedia courseware

teaching process

First, review the introduction:

1. In an equation, there are only addition and subtraction or only multiplication and division. What is the calculation order? for instance

2. An equation includes addition, subtraction, multiplication and division. In what order? for instance

There are brackets in the expression. In what order? for instance

4. Today we are going to learn "four operations". What exactly are the four operations?

Summary: Addition, subtraction, multiplication and division are called four operations. The mixed operation we learned before is the four operations.

Second, explore new knowledge.

Example 4: 96 ÷ 12+4× 2

1, tell me the operation sequence.

2. If parentheses are added on the basis of 96÷ 12+4× 2 to become 96÷( 12+4)× 2, what is the operation order? (Count what's in brackets first)

96÷( 12+4)× 2

=96÷ 16× 2

=6× 2

= 12

3. If brackets "]" are added on the basis of 96 \\( 12+4)×2, it becomes another formula of 96 \\( 12+4)×2. What is the operation sequence? Note: There are both brackets and brackets in an expression, so count the brackets first, then the brackets.

96÷[( 12+4)× 2]

=96÷ [ 16×2]

=96÷ 32

=3

4. Read "Do you know?"

5. Summary: Operation sequence:

(1) In the formula without brackets, if there is only addition and subtraction or only multiplication and division, it should be calculated from left to right.

(2) There are multiplication, division, addition and subtraction in the formula without brackets, and multiplication and division must be calculated first.

(3) If there are brackets in the formula, count the brackets first.

Third, consolidate the practice.

1, do it

2. Multiple choice questions:

What is the quotient of the sum of (1)47 and 33 divided by the difference between 36 and 16? The correct formula is ()

a、47+33÷36- 16 B 、( 47+33)36- 16 C 、( 36- 16)47+33

(2) What is the product of 750 minus 25 times 20 plus 13? The correct formula is ()

a 、( 750-25)×(20+ 13) B 、( 20+ 13)×(750-25) C、750-25×20+ 13

Fourth, class summary.

Four operations of blackboard writing design with brackets

96÷[( 12+4)× 2]

=96÷ [ 16×2]

=96÷ 32

=3