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20.04.2020 10:24
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When I came home from school, without a book, I smiled and dragged my mother in the kitchen, trying to "fish" some "benefits"-go to the bookstore to buy books. "Ding Ding!" The phone rang before Mom's "good" word was spoken. It turned out to be a question every day. My mother looked at it and turned her eyes. She smiled and said, "You do the right question and take you to buy a book immediately! A free meal is also included ~" I thought about it if I thought: It ��s still the previous question type, so I ��m sure it works! There are also attractive ��gifts��, and I agreed. My mother wrote down the question, and when I read the question, I was ignorant. This is the type of question I have not been exposed to: 36 students are reading books in the school reading room, of which 4/9 are girls, and then several girls At this time, the number of girls accounted for 9/19 of the total number of girls. Later, how many girls came to read the book? I stared blankly at the subject, and my brain was blank. 'S mother: "Mom, do you have any tips? Open a back door ~" She cleared her throat and pretended to ask me to think about it. I pouted, lowered my head, and reviewed the question again. Five minutes later, I had no clue, and mumbled: "36 people, 4/9 girls, then 9/19 ... ten minutes later Cheap Cigarettes, I still wanted to read books, but I did n��t think carefully. Clear. I grabbed my hair helplessly and asked for help again. I took my mother ��s hand, shook it and shook it, and said attentively: "Dear mother, beautiful mother, please do well. Prompt? "Mother really shaken, thought for a while, and said:" Oh, I can't see it anymore, let me tell you. Think about it, who has n��t changed when the girl changed? ��Who has n��t changed? Haha, it ��s a wake-up call. The girl has changed, the total number has changed, and the number of boys has n��t changed. Boys get started! It is known that "36 students are reading in the reading room, of which girls account for 4/9", and the original total number is regarded as the unit "1", which is divided into 9 parts on average, and girls are 4 of them. It accounted for 5/9 of the original total number, and the boys had 36 �� 5/9 = 20 (person). According to ��then several girls came later, the number of girls accounted for 9/19 of the total number�� Marlboro Lights, the current total The number of people is regarded as the unit "1", and the average is divided into 19 parts. The girl is 9 of them, and the boy has 10 such. Although the total number of people has changed before and after, the number of boys has always remained the same. "20 people" corresponds to "the male student accounts for 10 copies of the current total number of people." Therefore, as long as 20 �� 10 = 2 (person), you can find the number of people who appear in one copy. Now there are 2 people in the copy, and 9 girls Copies, now girls have 2 �� 9 = 18 (persons), and there are girls 36 �� 4/9 = 16 (persons) Cigarettes For Sale, using 18-16 = 2 (persons) to find out the girls who come later The number of people. Such a simple invariant is hidden in it, I did n��t find it, it really should n��t be! I secretly blamed myself, but my mother is still very happy to say: "Not bad, it ��s all right! I still take you Go buy a book! It ��s better if you do n��t need to dial it next time! ��He said, and he touched my head. Never start with a variable! Haha, through this question, I learned both new ideas and new ways to understand the question And I got my wish, got a lot of love books, and ate a meal in the "Pizza Hut" life. Mathematics is everywhere. Mathematics contains many mysteries of knowledge, waiting for us to continue to explore and discover. |
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