Teaching objectives:
(1) On the basis of students' understanding of addition and subtraction of fractions with the same denominator, students can further master the rules of addition and subtraction of fractions with the same denominator.
(2) Can skillfully calculate the addition and subtraction of fractions with the same denominator.
(3) Improve students' interest in learning mathematics through various exercises.
Teaching emphasis and difficulty: Skillfully calculating the addition and subtraction of fractions with the same denominator.
Preparation of teaching AIDS and learning tools: small blackboard or projector or multimedia, draft paper.
Teaching process:
First, basic training
1, oral calculation. (Answer by name directly)
1/3+ 1/3= 2/5+ 1/5= 3/7+4/7= 2/ 1 1+5/ 1 1= 6/7-5/7= 3/4- 1/4=
5/9- 1/9= 7/ 12- 1/ 12= 7/8+ 1/8= 2/3- 1/3= 9/ 10-3/ 10= 5/6+ 1/6=
2. Take the formula in the above question as an example to talk about arithmetic and calculation methods.
2/11+5/1means ()111plus ()1/.
5/9- 1/9 means () 1/9 minus () 1/9, leaving () 1/9, which is ().
3/7+4/7 means three () plus four (), and one * * * is seven (), that is, ().
9/ 10-3/ 10 means nine () minus three (), and six () is ().
Second, introduce doubts and explore new knowledge.
1. Doubt: We have understood the addition and subtraction of fractions with the same denominator and mastered the calculation method. If we add another number, will you count? Let's add a denominator to any oral calculation problem just now, add or subtract the scores with the same original scores, and try to calculate it.
2. Students make up questions and try to calculate.
(1) Students choose any topic and try to make up the calculation.
(2) Calculation method of deskmate communication.
Teachers should pay attention to students' possible calculation methods:
One is to calculate one by one;
The second is simultaneous calculation.
(3) Feedback typical topics, give names to roles, and talk about algorithms and methods.
(4) Teachers and students agree on the writing format.
3. Exercise:13/15+4/158/11-3/1.
(2) Discussion: What should be the score of a molecule of 0?
4. Summary: Addition and subtraction operations and methods of fractions with the same denominator.
Third, consolidate the practice.
1, practice. 1/6+2/6+3/69/ 10+3/ 10+7/ 10
16/ 17-5/ 17- 1 1/ 177/8-3/8- 1/8
(1) Students' independent calculation;
(2) talk about arithmetic and calculation methods, and discuss the treatment of results.
2. Judge whether the following calculation is correct. (indicated by gesture)
( 1)5/9+2/9+8/9= 15/27=5/9..............................()
(2) 17/20+ 1 1/20+7/20=35/20=7/4........................()
(3) 13/ 14-3/ 14-5/ 14=2 1/ 14=3/2= 1 1/2.....................()
(4)4/5- 1/5-3/5=0/5..........................................()
3. Fill in the appropriate number in (). (you can expand it appropriately to see who fills in more)
4/()+5/()+ 1/()= 1()/ 15-()/ 15-()/ 15=0
()/8+()/8-()/8=0()/9-()/9+()9= 1
Fourth, class summary.
1. Students talk at the same table first.
2. Name feedback.
Key points: (1) Addition and subtraction methods of fractions with the same denominator.
(2) General requirements for result processing.
Verb (abbreviation for verb) class assignment
1, oral calculation.
2/3+2/3+2/3 13/ 15+7/ 15+ 1/ 1523/30-7/30- 1 1/30 1 1/ 12-8/ 12- 1/ 12
2. Application exercises. (Pay attention to the handling of company names)
(1) Jane read a story book. On the first day, she read 5/ 16, the next day, she read 3/ 16, and the third day, she read 7/ 16. How many parts of the book did the Duke read in three days?
(2) The canteen burns 8/9 tons of coal in three days, 3/9 tons of coal in the second day of the first grade, and how many tons of coal on the third day?
3. "exercise book"
On the basis of the last lesson, students can easily master this content. The problem is that some students often don't simplify the calculation results or turn them into fractions.