Đáp án:
Công thức tính số góc tạo ra bởi `n` tia chung gốc là ` (n(n-1))/2`
Ta có ` (n(n-1))/2 = 1275`
` => n(n-1) = 2550`
` n;n-1` là hai số nguyên liên tiếp `
Mà `2550 = 50.51`
` => n = 51`
50
Giải thích các bước giải:
Có \(n\) tia chung gốc Suy ra: Số góc được tạo thành: \(\frac{n(n+1)}{2}\) góc Theo đề: \(\frac{n(n+1)}{2}=1275\) \(\leftrightarrow n(n+1)=2550=50.51\)\(\leftrightarrow n=50\)Vậy số tia chung gốc là 50 tia
I. Choose the word whose underlined part is pronounced differently from the others. 1. a. pottery b. product c. workshop d. conical 2. a. surface b. layer c. frame d. birthplace 3. a. weather b. thread c. together d.rather 4. a. historical b. system c. landscape d. business 5. a. carved b. impressed c. embroidered d. weaved II. Choose the word that has the main stress placed differently from the others. 1. a. craftsman b. attraction c. museum d. department 2. a. embroider b. lantern c. impress d. desire 3. a. workshop b. remind c. outskirts d. village 4. a. competition b. generation c. conical d. authenticity 5. a. family b. typical c. grandparents d. embroider III. Choose the underlined word that does not receive stress. 1. We shouldn’t build cable car system in Son DoongCave. A B C D 2. IsBen Thanh Market a place of interestin Ho Chi Mlnh City? A B C D 3. Many internationaltourists are interested in making woven baskets. A B C D 4. I picked up apiece of wood and started carving. A B C D 5. Lam and hisfriends often go to the cinema to enjoy the new films. A B C D 6. They were walking through Nguyen Hue Avenuewhen an accident happened. A B C D 7. Touristscan’tenter the War Remnants Museum after 10pm. A B C D IV. Choose the best answer a, b, c or d to complete the sentence. 1. The museum has a superb collection of ancient from Nubia. a. artefacts b. leather c. presence d. beads 2. Our aim is to make the performing arts, museums and our accessible to all. a.love b.patriotism c.heritage d.status 3. I have ten pictures and eight pieces sculpture on exhibition. a.of b.on c.in d.for 4. David Ferris’s father was a bank manager living the outskirts ofthe Lancastrian town of Preston. a.of b.on c.in d.at 5. All people should join hand in protecting the environment we can gainbetter health. a.in order that b. when c.because d.even though 6. we were waiting, a woman with a phone on her hand asked us what wewere doing. a.That b.In order that c. While d.Although 7. The bus uppassengers outside the airport. a.hits b.sends c. lays d.picks 8. After visiting Van Phuc village, they came to their hotel for lunch. a.at b.up c. down d. back 9. A: I’ll pick you up at eight o’clock on my way to the airport. B: a.For pleasure b. Great. I’ll see you then. c. I have a phone. d. Would be. 10. A: Would you like to join us on the trip to La Khe Silk Village? B: a.Sounds great. b. For now. c. Better things happened. d. I don’t think so. V. Write the correct form or tense of the verbs in brackets. 1. You can’t really have seen a UFO! You (imagine) things! 2. Linda was busy when we (go) to see her yesterday. She (study) for an exam. 3. The festival is held by the Hanoi City Department of Tourism (preserve)and develop traditional trade villages in Hanoi. 4. The owner of Hakata Traditional Craft and Design Museum (close)it down because of dropping profit. 5. Conical hat making (be) a traditional craft for hundreds of years. 6. The building (complete) at the end of last month. 7. Individuals should be responsible for (revive) local culture. 8. (you/ ever/ be) to Bat Trang Ceramic Village? VI. Write the correct form of the words in brackets. 1. The price of clay, supplies and equipment is a small percentage of the total cost to pottery. (product) 2. He started the youth group to keep local off the streets. (young) 3. Poem conical hats are believed to come from Tay Ho Village in Hue, which was famousfor hat makers. (skill) 4. Today, Hang Trong paintings are found only in museums or fine angalleries. (authenticity) 5. Craft village tourism has also proved an , receiving great attentionfrom visitors, especially foreign tourists. (attract) 6. Mass started in 1989 when the first 340 Windsurf guests arrived. (tour) 7. The tribe is concerned with the of its culture and traditions, (preserve) 8. The second collection was more decorative, inspired by and pattern. (embroider) 9. Vietnamese people have a strong desire to maintain a distinct identity. (culture) 10. I’d like to thank everyone for helping to make this day for us. (memory)
Ghép lại thành 1 câu hometown / large / town / his / a / is /. => is / city / busy / the /. => once a month / go / I / fishing /. => twice a week / she / rides / to school / a bicycle /. => sometimes / go camping / we / at the weekend /. =>
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