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Hai kệ sách tất cả chứa 120 cuốn sách .
Chuyển 20 cuốn sách từ kệ thứ nhất sang kệ thứ hai.
Chuyển 30 cuốn sách từ kệ thứ hai sang kệ thứ nhất.
Hai kệ bây giờ có số sách bằng nhau.
Có bao nhiêu cuốn sách trên mỗi kệ lúc đầu?
Giải
Chuyển 20 cuốn sách từ kệ thứ nhất sang kệ thứ hai và chuyển 30 cuốn sách từ kệ thứ hai sang kệ thứ nhất tức là chuyền 10 cuốn sách từ kệ thứ hai sang kệ thứ nhất thì số sách ở hai kệ bằng nhau.
Suy ra lúc đầu kệ thứ hai hơn kệ thứ nhất là : 10+10=20 (cuốn sách)
mà tổng số sách ở hai kệ là 120 cuốn
=> Số sách ở kệ thứ nhất là : (120-20):2=100:2=50 (cuốn)
<=> Số sách ở kệ thứ hai là : 120-50=70(cuốn)
Vậy kệ thứ nhất có 50 cuốn sách và kệ thứ hai có 70 cuốn sách
Hai kệ bây giờ có số sách bằng nhau.
Chuyển 30 cuốn sách từ kệ thứ hai sang kệ thứ nhất.
Chúc bạn học tốt
Có 40 quả trứng chia làm 2 thùng. Nếu chuyển 5 quả trứng từ thùng thứ nhất ra thùng thứ 2 thì thùng thứ 1 sẽ hơn thùng thứ 2 2 quả trứng . Tìm số trứng ở thùng thứ 2 lúc đầu. ( dịch sơ qua thôi )
Bạn tự giải đi . Hihi
I.Use the words given and other words, the second sentence so that it has a similat meaning to the first sentence.
1.The lamp is behind the computer
=> The computer is in front of the lamp.
2.There is an air- conditioner and a ceiling fan in our living room
=> Our living room has an air-conditioner and a ceiling fan.
3.Peter's house isn't far from the station
=> Peter's house is near the station.
4.The dog is to the left of the sofa and to the right of the wardrobe.
=> The dog is between the sofa and the wardrobe.
5.Tom’s bedroom has two bookshelves.
=> There are two bookshelves in Tom’s bedroom.
II.Rewrite the following sentences so that it has a similar meaning to the first sentence
1.I don't have my bookshelf in my bed room.
=> There aren't any bookshelf in my bedroom.
2.Is there a computer rooom at your school?
=> Does your school have a computer room?
3.Both Maths and English are interesting to him.
=> He is interested in both Maths and English.
4.Hoa's school has more than 500 student.
=> There are more than 500 students in Hoa's school.
5.Janet doesn't like watching sport on TV.
=> Janet is not keen on watching sport on TV.
In 1783, two French brothers built the first balloon to take people into the air. One hundred and twenty years .later.., in 1903, the Wright brothers built the first plane with an engine and flew in it. This was .in.. the United States. Then, in 1918, the US Post Office began the first airmail service.
Aeroplanes changed a lot in the next thirty years. Then, in the 1950s, aeroplanes became much .faster.. because they had jet engines.
In 1976, Concorde was built in the UK and France. It was the fastest passenger plane in the world at that time and it .can.. fly at 2300 kilometres an hour, so the journey from London to Newyork was only four hours.
Today, millions of people travel .by.. aeroplane, and it is difficult to think of a world without them.
1. How many people are there in your family?
→ How many_________people does your family have?_____________________________________________
2. The bakery is to the left of my house.
→ My house ...is to the right of the bakery...............................................................................................
3. Mr Minh has a son, Trung.
→ Mr Minh .........is Trung's father..........................................................................................
4. Trang is riding her bike to school.
→ Trang is going .........to school by bike..................................................................................
5. Huyen walks to school every afternoon.
→ Huyen goes ...........to school on foot every afternoon....................................................................................
6. Does your class have forty students?
→ Are .........there 40 students in your class.................................................................................................. ?
7. That motorbike belongs to Mr Trung.
→ That is .........Mr Trung's motorbike .............................................................................................
8. Does your father cycle to work?
→ Does your father get ........to work by bicycle?......................................................................... ?
Bài 1: First task:
Let \(x\) be the number of sparrows on the first lamp post at first. (\(x\) is a positive integer).
\(\Rightarrow16-x\)is the number of sparrows on the second lamp post at first.
We have: \(x-2+3=16-x+2-3\Leftrightarrow2x=14\Leftrightarrow x=7\)
Hence there are 7 sparrows on the first lamp post at first, 9 sparrows on the second lamp post at first.
Bài 2: Second Task
We can find 2 students who were born on the same day.
There are 30 days in April and 31 students were born on that month. Apply the Dirichlet 's theorem, we can ensure that threre exists at least one day where 2 students were born.