2m/s = 7,2 km/h
1h30'=1,5h
Vận tốc khi thuyền xuôi dòng là:
v1=18 + 7,2 =25,2 (km/h)
Thời gian thuyền đi xuôi dòng ( A -> B )
t1 = sAB / 25,2 (h)
Vận tốc thuyền đi ngược dòng là:
v2 = 18 - 7,2 =10,8 (km/h)
Thời gian thuyền đi ngược dòng ( B -> A)
t2 = sAB / 10,8 (h)
t1 + t2 =1,5
=> sAB / 25,2 + sAB / 10,8 = 1,5
Giải phương trình trên ta được
sAB = 11,34 (km)

Việt Nam Quốc dân đảng là chính đảng theo khuynh hướng chính trị nào?

A. Quốc gia cách mạng tư sản 

B. Quốc gia cải lương tư sản

C. Quốc gia tư sản  

D. Quốc gia dân tộc tư sản

ko zì gọi là miễn phí đâu các pạn ạ!

1.Will they come ( thay / come ) tomorrow ?

2. When will you get ( you / get ) back ?

3. If you lose your iob , what will you do ( you / do ) ?

4. In your opinion , will she ( she / be ) a good teacher ?

5. What time will she sunset ( the sun / set ) today ?

6. Will she get ( she / get ) the job , do you think ?

7. Will david be ( David / be ) at home this evening ?

8. What will the weather like ( the weather / be ) like tomorrow ?

9. There's someone at the door , will you get ( you / get ) it ?

10. How will he get ( he / get ) here ?

1.your/What/doing/mother/is/?

What is your mother doing ?

2.cooking/is/kitchen/she/in/the.

She is cooking in the kitchen .

3.doing/are/What/you/?

What are you doing ?

4.cleaning/the/floor/I/am.

I am cleaning the floor .

5.your/doing/What/is/brother/?

What is your brother doing ?

6.reading/a/book/he/is/new.

He is reading a new book .

1. Tuan and his brother ( not watch ) aren't watching TV at the moment . They ( be ) are asleep .

2. My father always ( come ) comes home late . He ( finish ) finisher work at 5 o'clock .

3. I ( not understand ) don't understand this sentense . What does this work ( mean ) mean?

4. Right now I ( look ) am looking around the classroom . Minh ( write ) is writing in his book .

5. Lien's friend (have ) has a new bike but he ( not like ) doesn't like it very much .

6. Where are your ( do ) doing now ? - I ( unload ) am unloading the vegetables .

7. Where are your children (be ) are ? - They're upstairs. They ( play ) are playing video games.

8. Is Nam ( work ) working in the garden at the moment ?

Từ etilen, viết các phương trình hoá học (ghi rõ điều kiện) điều chế các chất sau : axit axetic, etyl axetat.