- 629 . ( 371 + 536 ) + 371 . ( 629 - 536 )

Một miếng hợp kim vàng - đồng có trọng lượng trong không khí là 0,567 N, trong nước là 0,514 N. Xác định tỉ lệ phần trăm vàng, đồng có trong hợp kim. Cho KLR của vàng D1= 19300 kg/m3, của đồng D2= 8900 kg/m3, của nước D = 1000 kg/m3 .

Do you ever think about what schools will be like in the future? Many people think that students will study most regular classes such as maths, science and history online. Students will probably learn these subjects anywhere using a computer. What will happen if students have problems with a subject? They might connect with a teacher through live video conferencing. Expert teachers from learning centres will give students help wherever they live. Students will still take classes in a school, too. Schools will become places for learning social skills. Teachers will guide students in learning how to work together in getting along with each other. They will help students with group projects both in and out of the classroom. Volunteer work and working at local businesses will teach students important life skills about the world they live in. This will help students become an important part of their communities. Some experts say it will take five years for changes to begin in schools. Some say it will take longer. Most people agree, though, that computers will change education the way TVs and telephones changed life for people all over the world years before. 27. What will happen if students meet difficulties with a subject? A. Teachers from learning centres will give them help through live video conferencing. B. They will meet their teachers in person for help with problems with the subject. C. They will telephone the teachers who are staying at the school to seek their help. D. Schools will organise a live video conference for teachers to help students with problems. 28. Students will still go to school to _____ . A. learn all subjects B. play with their friends C. use computers D. learn social skills 29. The main role of teachers in the future will be _____ . A. providing students with knowledge B. guiding students to learn computers C. helping students with group projects D. organising live video conferences 30. Students will learn important life skills through _______ . A. going to school every day B. taking online classes C. working in international businesses D. doing volunteer work 31. What is the main idea of the passage? A. Kids won’t have to go to school in the future. B. Computers will change education in the future. C. All classes will be taught online in the future. D. Teachers will help students from home in the future. 32. Let’s face _____ we are destroying the environment and we need to do something now. A. truth B. facts C. things D. information

Face-to-face conversation is a two-way process: You speak to me, I reply to you and so on. Two-way (22)_______ depends on having a coding system that is understood by both sender and (23)_______, and an agreed convention about signaling the beginning and end of the message. In speech, the coding system is the language like English or Spanish; the convention that one person speaks at a time may seem too obvious to mention. In fact, the signals (24)_______ in conversation and meetings are often (25)_______. For example, lowering the pitch of the voice may mean the end of a sentence, a sharp intake of breath may signal the desire to interrupt, catching the chairman’s eye may indicate the desire to speak in a formal setting like a debate, a clenched fist may indicate anger. When (26)_______ visual signals are not possible, more formal signals may be needed. 22: A. Exchange B. Interchange C. Communication D. Correspondence 23: A. Announcer B. Receiver C. Messenger D. Transmitter 24: A. That people use B. Are used C. Using D. Being used 25: A. Informal B. non-verbal C. verbal D. formal 26: A. their B. These C. This D. That

tìm giá trị âm đầu tiên trong mảng một chiều các số thực. nếu mảng không có giá trị âm thì trả về giá trị không âm là 1

33. She didn’t hurry, so she missed the train. => If………………………………………………………………………. 34. Barbara is the best tennis-player in the club. => No one………………………………………………………………… 35. I haven’t seen that man here before. => It’s…………………………………………………………………….. 36. The furniture was so expensive that I didn’t buy it. => The furniture was too…………………………………………………. Complete the second sentence so that it has a similar meaning to the first one using the word in brackets. Do not change the given words in any ways 37. The robbers made the bank manager hand over on the money. (WAS) ……………………………………………………………………………………………………………….. 38. Tom learned to drive when he was nineteen. (SINCE) ……………………………………………………………………………………………………………….. 39. She had never been so unhappy before. (THAN) ……………………………………………………………………………………………………………….. 40 It was so late that nothing could be done. (TOO) …………………………………………………………………………………………………

Hai vật có khối lượng m1 = 200 g và m2 = 300 g, có thể chuyển động không ma sát nhờ đệm không khí. Lúc đầu vật thứ hai đứng yên, còn vật thứ nhất chuyển động về phía vật thứ hai với vận tốc 44 cm/s. Sau khi va chạm, vật thứ nhất bị bật trở lại với vận tốc có độ lớn 6 cm/s. Tính vận tốc vật thứ hai sau khi va chạm.

Tính D = 10 + 12 + 14 + ... + 994 + 996 + 998 Nhận xét: Các số hạng của tổng D đều là các số chẵn, áp dụng cách làm của bài tập 3 để tìm số các số hạng của tổng D như sau:

tìm số hoàn thiện đầu tiên trong mảng một chiều các số nguyên, nếu mảng không có số hoàn thiện thì trả về -1

Một ô tô khối lượng 1 500 kg đang chạy thì đâm phải một bức tường và bật trở lại trong thời gian 0,15 s. Vận tốc ô tô trước và sau khi va chạm có độ lớn lần lượt là 15 m/s và 2,6 m/s. Tính xung lượng và cường độ lực trung bình do tường tác dụng lên ô tô. Bỏ qua mọi ma sát.