Math diary Grade 5 Grade 2 (Buy Oranges) Time: 2010 065438+10.021Math is everywhere in life. For example: buy food! Buy stationery! Measuring cloth, etc. , all need to use mathematics. This semester, the teacher taught a new knowledge, that is, the multiplication and division of decimals. This knowledge helps me a lot! Last night, my mother went to buy oranges together. A kilo of oranges 1.8 yuan. My mother bought 4.5 kg and should pay 8. 1 yuan. But the clerk was careless and didn't know how to calculate it, so it became 9 yuan money. Fortunately, this semester, I used the knowledge of Protestantism, and after doing a calculation in my mind, I immediately corrected the salesman's mistake. Not only did my aunt, the shop assistant, praise me for my cleverness and my ability to multiply and divide decimals in such a small city, but my mother also praised me for saving her 0.9 yuan on the way home, and the knowledge I learned can be applied in my life. Yes! If you don't learn this math well, it's not only 0.9 yuan that will lose, but also hundreds, thousands or even hundreds of millions! Math diary, Grade Five, Grade Three (Story of Buying Medicine) Time: 201065438+1On Sunday morning of October 22nd, my grandfather and I went to the Lotus Pond drugstore and bought two boxes of pills-two boxes of Weiershu 44 yuan and one box of 22 yuan. Grandpa gave her 50 yuan, and the salesman gave it to Grandpa 6 yuan. After I found the change, I calculated it with decimal addition and subtraction. Grandpa can also pay like this: 1. Give it to 40 yuan, the shop assistant, and then pay 5 yuan. The asking price is 1 yuan. 2. If Grandpa has change, he can pay 40 yuan first and then 4 yuan. By buying medicine with grandpa this time, I know that mathematics is closely related to our lives. Another time, my sister and I went shopping in the supermarket. I bought a pack of beef jerky, a bottle of milk and a bottle of soda. 10 yuan. Zhao Lin bought a box of biscuits, a bottle of soda and a piece of 9 yuan money. We gave the shopkeeper 20 yuan money. The shopkeeper gave us 2 yuan money. When we were ready to go home, Zhao Lin said, "I still want to buy 10 bubble gum." I took out the money and found that the shopkeeper gave me 1 yuan. Let's go back and return the extra 1 yuan to him. The shopkeeper praised us as an honest boy, and our hearts were filled with joy.