Đáp án: Số đo cung của hình quạt tròn là $320^o$

Giải thích các bước giải:

  Ta có: $S_{quạt}=\dfrac{\pi.R.n}{360}$ 

        ⇒ $\dfrac{32\pi}{9}=\dfrac{\pi.4.n}{360}$ 

       ⇔ $n=320^o_{}$ 

Vậy số đo cung của hình quạt tròn là $320^o$

B.

I. Rewrite the following sentences so that the second sentence means the same as the first one.
1. Scientists have invented  new devices to help people live a longer life.
  New devices ………………………………………………………………….………………………
1. I don’t have enough time, so I can’t go on holiday this summer.
 If  I had ….………………………………………………………………….………………………..
3/The man had a broken leg. He tried to save his wife.
-In spie of………………………………………………………………………………….…………
4. I can’t tell you because I don’t know the answer.
-If I knew ….……………………………………………………………………………………..…
5. They will do the test well. They will review them all hard.
-->If………………………………………………………………………………………………………
6. The rescue workers evacuated the villagers in the raged flood to the safe place last night.

The villagers in the raged flood………………………….………………………………………………..
7. The students will provide aids for the homeless people tomorrow.
-->Aids…………………………………………………………………………………………………..…
8. The people will protect the environment now. The environment will be nice.
If…………………………………………………………………………………………………………
9. They don’t have a map, so they get lost.
  If…………………………………………………………………………………………..……………
10. The storm destroyed many houses in this village last week.
-->Many houses………………………………………………………………………………….…………
11. Did they give food to homeless people last year ?
-->Was food ………………………………………………………………………………………………..…
12. Although the weather was bad, the football match was not canceled.
-->Despite ………………………………………………………………………………………………..………
13. The people will protect the environment now. The environment will be nicer.
If…………………………………………………………………………………………………….……
14. They don’t have a map, so they get lost.
If………………………………………………………………………………………………….………
15. The storm destroyed many houses in this village last week.
-->Many houses………………………………………………………………………………………….…
16. Many rivers and lakes are poisoned. Factories produce waste and pour it into rivers and lakes. 
Because ……………………………………………………………………..…………………………
17. Plastic bags are a major source of waste. We should not throw plastic bags everywhere. (so)
…………………………………………………………………………………………………………….
18. We won’t hold the festival. It costs too much money. (IF)
=> …………………………………………………………………………………………………………
19. “ How do you think people on Venus communicate?”  Edward said to his friend.
Edward asked his friend ………………………………………………………………………………..
20. “ I will hand in my assignment to  the teacher tomorrow.” 
She said ……………………………………………………………………………………………………
II/ Give the correct tense or form of the following verbs.
 1. I (watch) ……………………. a science fiction film on TV at 9 .00 tonight.
2. Our teacher says that new technology (make)…………. many workers jobless in the future.
3. Look at those clouds – I think it (rain)…………..………..
4. If you use robots  to do the housework, you (become)…….. lazy and you (not get)…………….. enough exercise.
5. People say that technology (change) ………… up entire rooms are small enough to put on destops and into wristwatches.      6. We’ll need (call)……….. him more often.
7. This time next week, I (lie)…………… on the beach on Phu quoc Island
8. Thomas Edison said that none of his inventions ( come)………… by accident. They (be)…………. all the result of hard work
9. By the time I( arrive)………the airport, my husband( wait)………………..for me for an hour.
10. If the trees(be not)……………………….watered daily, they will die.

11. Air pollution (be) …………………………….. not good for our health.
12. Many houses ( destroy)………………………in the hurricane last night in Nghe An.
13. If the students reviewed all lessons, They(do)…………………..the test well.
14. After the thief(leave)…………………….the house, the police (come)…………………..
15. He ( not go )……………….. out last night, he ( stay )……………………….. at home.
16. ………. Lan ( learn )……….… English for 2 years ? - No, she ( learn )…………………. for 3 years.
17. …….you ( wear )…… uniform yesterday ? No. I ( not wear )……. yesterday.
18.….your mother ( read )……… book every night ? - No, she ( watch ) …………………TV.
19. We (save)  ________________electricity if we didn’t pay much money.
20. If we use water carefully, more people (have) ______________fresh water.
21. That room (paint)………………………………at this time next week.
22. He wouldn’t be ill if he (smoke)________________  a lot.
23. By the time the police (come)…………………….., the thief (leave)………….……………
24. After I(finish)…………………..the lesson, Lan went out.
25. This house ( build)……………..…………. in 2015.