Hua, a famous mathematician, once said: "The universe is big, the particles are tiny, the speed of rockets, the cleverness of chemical industry, the change of the earth, the mystery of biology, and the complexity of the sun and the moon are everywhere." Especially in the 2 1 century, the application of mathematics is everywhere.

It's rare to have a holiday today, so I took my parents shopping when the interest class had a holiday. Actually, it's more about helping me buy books than shopping!

My parents also read my mind and said, "it is ok to buy books, but you have to work out the discount price of books." How about it? " I readily agreed.

The first book I want to buy is Aesop's Fables. The price of this book is 10 yuan, but because it is a holiday, I should get a 10% discount, so I should multiply it by 0. 9, but I haven't learned to multiply numbers with decimal points, so I want to use simple calculations. "Oh, yes, you can put 0. 9 as 1, then 10x 1 = 10 is 10 ÷10 =1,and then use1. Dad smiled and said, "What about 20 yuan for a book? "Yes, if it is not an integer, wouldn't it be hard to forget? So, I thought hard again. : "hey, I know! "You can put 0. 9 expand 10 times, that is, 9, and then use 9X20 = 180. Because we expanded 10 times in the calculation, we need to reduce 10 times now, that is, 180 ÷ 10 = 18 (yuan

So I told my dad with confidence. This time, my dad showed a approving smile! I also got the book I wanted.

This made me really understand Hua's famous saying. I think: with the growth of grade, you must know how to make full use of what you have learned in class in your life in order to further improve your grades!