Cho số nguyên dương 𝑛. Yêu cầu: Đếm số cặp (𝑎, 𝑏) sao cho 1 ≤ 𝑎, 𝑏 ≤ 𝑛 và 𝑎 chia hết cho 𝑏.

Dữ liệu vào: đọc từ file văn bản GCDAB.INP số nguyên dương 𝑛(𝑛 ≤ 1012).

Kết quả: Ghi ra file văn bản GCDAB.OUT một số nguyên dương là số cặp (𝑎, 𝑏) thỏa mãn yêu cầu đề bài.

Ví dụ: GCDAB.INP

3

GCDAB.OUT

5

Giải thích: Có 5 cặp (𝑎, 𝑏) mà 1 ≤ 𝑎, 𝑏 ≤ 3 và 𝑎 chia hết cho 𝑏 là (1,1), (2,1), (2,2), (3,1), (3,3).

 code c++ ạ

* Choose the best answer

1. She is good ______________ meteorology.

A. on B. in C. at D. for

2. Last night, volcano Maui ______________ and the large areas of land were affected.

A. erupts B. erupted C. erupting D. erupt

3. I _______ buy things online, just once or twice a year. I prefer to shop at the shopping mall.

A. rarely B. always C. usually D. often

4. My sister _______ watches the Junior Master Chef programme. She never misses an episode.

A. seldom B. never C. rarely D. always

5. People go to a shopping centre for many ______.

A. people B. thing C. reasons D. product

6. Con Dao National Park plays a key role in saving the ______.

A. small islands B. environment B. water D. air

7. She’s a _______. She spends too much time and money shopping.

A. worker B. student C. shopaholic D. farmer

8. A ______________ often occurs in the mountainous areas because many trees have been cut down.

A. forest fire B. flood C. tornado D. landslide

9. When there is a _______ , hot gases and liquid rock pour out from a mouuntain.

A. tornado B. storm C. earthquake D. volcanic eruption

10. People enjoy ______ for one or two hours in clean and well-lit areas.

A. walking B. walk C. have D. having

11. They ______________ on the lake when it started to rain, so they went home.

A. fished B. fishing C. were fishing D. are fishing

12. Her dad found some money while he ______________ her suitcase.

A.packing B. package C. are packing D. was packing

13. Your brother ______________ in Myanma when he met his girlfriend.

A. study B. was studying C. were study D. was study

14. Ba: Were you having dinner at 6 p.m yesterday?

Nam: _______

A: No, I didn’t . C: Yes, I was.

B: Yes, I did. D: No, I don’t.

15. Her mom ______________ in the park when she saw a rabbit.

A. was going B. was going C. were going D. were going

16. _______it _______ when you woke up this morning?

A.Is...raining B. Was...raining C. Is...rain D.Were.. . rainin

17. What ______________ when his mother came?

A. were you doing B. was you doing C. are you doing D. are you doing

18. Don’t forget to turn off the lights ____ you go out.

A. after B. before C. till D. until

19. He ______ a sandwich when his phone rang.

A. is eating B. eats C. was eating D. ate

20. It ______________ when I left Ireland.

A. was rain B. was raining C. is raining D. raining

21. Andrea lives next door, so we ____________ see her.

A. never B. often C. rarely D. seldom

22. We should avoid dumping waste ____ lakes and rivers to reduce water pollution.

A. on B. into C. out D. by

23. Americans throw ___________ twenty-eight and a half million tons of plastic in landfills every year.

A. in B. at C.to D. away

24. Residents in tall buildings in Ha Noi ran _____ their homes in fear.

A. out of B. on C. to D. out

25. Con Dao National Park ______ a rich habitat for marine life.

A. releases B. reduces C. provides D. reuses

26. The roads were slippery ___________ it started to rain.

A. so B. as soon as C. when D. before

27. My grandmother ____________ goes to the market to buy food. She goes there every day.

A. always B. never C. rarely D. sometimes

28. Do you like ____________ products?

A. home-growing B. home-grew C. home-grown D. home-grow

29. _______ trees and burning forests destroy a lot of wildlife habitats.

A. Watering B. Cleaning up C. Planting D. Cutting down

30. Do you know that ____ can cause pollution?

A. littering B. releasing C. protecting D. keeping

31. You can _______ bargain at the supermarket because the prices are fixed.

A. always B. often C. never D. sometimes

32. There were only a few houses left standing _____ the tornado hit.

A. after B. before C. as soon as D. until

33. The shuttle bus ____ every 15 minutes to take customers to the parking lot.

A. will leave B. leaves C. left D. was leaving

34. We _____ home economics next semester. We have music instead.

A. didn’t have B. won’t have C. don’t have D. weren’t having

35. The announcement says that the sale _______ for just two hours, from 17:00 to 19:00 tomorrow.

A. lasts B. will last C. lasted D. last

36. Phong: My uncle called this morning. A flood destroyed his house. Mark: ________

A. I’m glad. C. You’re welcome.

B. I’m sorry to hear that. D. You’re very kind.

37. What were you doing when the volcano _______ ?

A. erupted B. erupt C. erupts D. was erupting

38. I ____ TV at 9 p.m yesterday.

A. didn’t watch B. don’t watch C. wasn’t watching D. isn’t watch

39. Water pollution can put negative _________ on our health.

A. contamination B. affects C. effects D. problems

40. Rescue _______ are trying hard to save people in the flooded area.

A. worker B. workers C. child D. children

Hỗn hợp khí A gồm NO,NO2 có tỉ khối so với H2 là 18.a)Tính khối lượng nguyên tố N có trong 28,8g hỗn hợp khí A b)Đạm ure có cthh là (NH2)2CO được dùng để cung cấp nguyên tố N cho cây trồng.Tính khối lượng Ure cần dùng để cung cấp 1 lượng N đúng bằng lượng N co trong 28,8gam hh A
Cứu em với em đang cần gấp , đề thi hsg hóa 8 2023-2024 huyện tiên du