"Ding" accompanied by the beautiful bell for class, Mr. Liu strode into the classroom. She said to us with a big smile, "In this class, we will learn the kilograms, grams and tons in Unit 3."

Then, Mr. Liu carefully took out a silver-gray balance and a green platform scale from the side. Then Mr. Liu conveniently picked up a bag of salt on Chen Yu's first row of clothes table, said, put the salt on the platform scale, and pointed to the pointer on the platform scale, let us carefully observe the successive changes of the pointer. At this time, Mr. Liu quickly grabbed a bag of salt and put it on the platform scale to guide us to continue to observe the changes of the platform scale. Under the guidance of Mr. Liu, we understand that the scale pointer without salt points to zero, while the scale pointer with a bag of salt points to 500 grams, and the pointer with two bags of salt points to 1000 grams.

Finally, Mr. Liu took out a penny and a paper clip and weighed them, which made us understand the use of the balance.

How time flies! The class will be over in the blink of an eye. I think this is really an interesting math class.