Transition: Students, in fact, there is something more precious in the world than Picasso's famous paintings, and that is time. If we don't cherish it, time will slip away quietly. How long will it take hundreds of millions?

The teacher has some exercise books here. At present, there are 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 ... How long will it take to produce hundreds of millions of exercise books at this rate? (Blackboard: hundreds of millions) Who will guess first? (Guess on the blackboard)

1. Now, let's discuss the design. How can we calculate by hands-on practice? (Students discuss and name) How many books are appropriate? (100)

2. One student in each group is responsible for timing, and other students count together to see how long it takes to count to 100. (90 seconds) How long does it take for each group to calculate hundreds of millions of books? (90000000 seconds) How long is 90000000 seconds? (Guess the name) How many years? Can you do the calculation with a calculator? Then how to calculate?

How many minutes is 90 million seconds? Then calculate the equivalent of how many hours? How many days is it equivalent? Equivalent to how many years?

The second of hundreds of millions of exercise books is equivalent to about three years. (blackboard writing: equivalent to 3 years) However, people have to eat and sleep, and 24 hours a day can't be used for accounting, so there can only be 8 or 9 hours a day at most? In that case, it will take nine years to calculate 100 million. In other words, everyone is 1 1 year old this year. Counting from now on, you can only count 100 million exercise books at the age of 20!

(3) How big is1100 million in terms of weight?

In the learning activities just now, everyone started with bold guesses, after careful hands-on practice, after careful calculation, and finally through comparative perception, they found a scale of 100 million, and they all succeeded. Next, we will study the weight of 100 million grains of rice by weighing rice.

1. Now let's look at the activity requirements:

① Discuss the steps of the activity first. ② Active participation and careful calculation. ③ Fill in the research record form carefully.

2. Now, please share the research results. (1 100 million grains of rice weigh about 2.5 million grams)

(1), China has a population of about1300 million. If everyone saves one grain of rice every day, how many grams of grain can the whole country save every day? 2500000× 13=32500000 (g)

(2) If everyone eats 400 grams of rice every day, how many days can one person eat the saved rice? About how many years? 32500000÷400=8 1250 (days) 8 1250÷365≈223 (years)

Student, enough for one person to eat for more than 200 years! There are so many people in China, if everyone saves a little, what an amazing number it is to get together! All the resources on this earth are limited, so each of us should start with saving a grain of rice, a piece of paper, a drop of water and electricity, and form a good habit of thrift.

Third, humanistic reading, deepen the experience

In the process of mathematics learning, we often need to consult some materials and data. Please read the following information now. How do you feel?

1 and 1 100 million drops of water can be combined into about 3333 liters of water, which can hold four large water trucks.

2. According to the financial announcement of China Mobile at the end of June 2004, the average daily net profit was 654.38 billion yuan.

Xinmin Daily, February 26, 2004. Up to now, more than 65438+ billion chickens have been slaughtered in Asia where bird flu broke out.

The earth is a young planet, and her age is about 4.6 billion years old.

5. Shenzhou VI spacecraft flew around the earth for about 5 days and then returned to the earth, flying nearly 3.4 billion meters.

Teacher: Please say how big 100 million is in the group.

Fourth, summarize the class and talk about the gains.

Teacher: What did you gain from this class today?

Students, the mystery of mathematics is endless. However, as long as you are brave in exploration and practice, there will be new discoveries and new gains!