1, which is probably widely used in daily life;
2. Estimation helps people to grasp the range of calculation results in advance, and provides a basis for judging whether the results of calculators, mental calculations and written calculations are reasonable;
3. Estimation is an important channel to develop children's sense of numbers, which is conducive to improving students' ability to solve problems.
At present, the focus of this cutting is to cultivate students' awareness of estimation and make students realize the necessity of estimation through appropriate situations.
In this session, I divide the children into four steps and count the beans myself:
1, grab: grab a handful of beans first (don't grab too much: the beans won't fall off when you turn your hand; Not too little: mainly because I feel my palms are full);
2. guess: guess how many beans there are in a handful (that is, what we call "estimation" in mathematics);
3. Number: Count an actual * * * (this is the knowledge of last class: it can be 1 1, it can be 2 2, it can be 10).
4. Comparison: Compare the estimated value with the actual value.
I first demonstrated the process of counting beans, and then let the children do it several times by themselves (the reason for doing it three times is that the children have no concept of estimation for the first time, and there will be a big gap between the estimated figures and the actual figures; The second time, you can use the last experience as a standard to re-estimate). In this link, the order in the classroom has been very good, and the children are seriously grasping, evaluating, counting and comparing. .....
In fact, the closer the estimated figure is to the actual figure, the higher the feeling of success, and the mood is naturally very happy and excited. This process is also very conducive to cultivating children's sense of numbers.