Trong lĩnh vực thủy lợi, mương được gọi là cái dạng “thủy động học” nếu với tiết diện ngang của mương có diện tích xác định, độ dài đường biên giới của nhỏ nhất. Cần phải xây dựng nhiều mương dẫn nước dạng “thủy động học”. Giả sử mương dẫn nước có tiết diện ngang là hình chữ nhật (như hình vẽ) với diện tích bằng 200 . Xác định kích thước của mương dẫn nước để mương có dạng “thủy động học”.                                

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Một số câu hỏi khác có thể bạn quan tâm.

• Blacken the lettre A, B, C or D on your answer sheet to indicate the correct answer to each of the following questions:         

  They missed the ferry. It ……………..by the time they reached the pier.         

• Blacken the lettre A, B, C or D on your answer sheet to indicate the correct answer to each of the following questions:

  He asked me…………..the film called “ Star Wars”.         

• Mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the following question:

  I _______ along the street when I suddenly heard footsteps behind me.  

• Mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the following question:

  He occasionally _______ a headache in the morning.         

• Mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the following question:

  "You should stop working too hard, _______ you'll get sick", she said.         

• Mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the following questions:

  Tuition fee must be paid____________ before or on the due date.    

• Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the following questions:

  "Those eggs of different colors are  so beautiful!" -  "Yes, they_____ in Russia"        

• Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the following questions:

  If you_____ so busy, I would have shown you how to play.         

• Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the following questions:

  The living conditions in the rural areas of the country ______ during the past five years.         

• Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the following questions:

  _____colleges and____universities are the main institutions that provide tertiary education.