Một trường học có 20 lớp trong đó 10 có 12 Lớp mỗi lớp có 20 học sinh và 8 lớp mỗi lớp có 25 học sinh hỏi trường đó có tất cả bao nhiêu học sinh

Cho số tự nhiên A= 7+ 7²+7³+7⁴+7mũ5+7mũ6+7mũ7+7mũ8 A)số A là số chẵn hay lẻ B)chữ số tận cùng của A là j C)số A có chia hết số 5 không

Cho một vật rắn chuyển động trên đường nằm ngang. Tính công cản và công phát động khi S = 10 m trong 2 trường hợp sau : a) Vật chuyển động thẳng đều. b) Vật bắt đầu chuyển động nhanh dần đều và đạt được vận tốc 4 m/s. Biết hệ số ma sát là 0,1 và vật đó có khối lượng là 2kg.

Câu 9: Để hòa tan hết 4,24 gam hỗn hợp Fe và FeO cần dùng hết m gam dung dịch HCl 18,25% thu được dung dịch A và 1,12 lít khí hiđro (đktc). a) Tính % khối lượng của từng chất trong hỗn hợp ban đầu. b) Tìm m và nồng độ % của muối trong dung dịch A.

tìm x thuộc z a,(3x+9)(11-x)=0

Một người kéo một cái thùng nặng 30kg trượt trên sàn nhà bằng một sợi dây có phương hợp với phương ngang một góc = 450, lực tác dụng lên dây là 150N. Tính công của lực đó khi hòm trượt được 15m? Và khi hòm trượt , công của trọng lực bằng bao nhiêu?

giải giúp em câu 1 và câu 2 với ạ. Em cần gấp! Em cảm ơn rất nhiều

hãy tưởng tượng và kề về hình ảnh mẹ khi em xa mẹ một thời gian dài

Cho m g hỗn hợp X gồm NaBr và CaCl2 vào đ AgNO3 dư, sau phản ứng thu được 2m g kết tủa (gồm AgBr và AgCl) . Tính % khối lượng mỗi kim loại trong hỗn hợp X.

1. The trees ________. A. were grown by John yesterday in the backyard​B. were grown in the backyard by John yesterday C. were grown in the backyard yesterday by John​D. in the backyard were grown by John yesterday 2. ________ to you yet? A. Are the book been giving back​​​B. Was the book been given back C. Has been the book given back​​​D. Has the book been given back 3. Portuguese ______ as an official language in this city since three hundred years ago A. has always been spoken​​​​B. had always spoken C. has always spoken​​​​​D. has been spoken always 4. All planes _____ before departure A. will checked​​​​​​B. will have checked​ C. will be checked​​​​​D. will been checked 5. Today many serious childhood diseases ______ by early immunization. A. are preventing​B. can be prevented​C. prevent​D. can prevent A. should control​B. controlling​C. would control​D. should be controlled 6. A story ______ by the teacher A. is going to be hold​B. will be tell​C. are going to be told​D. is going to be tell 7. This house ______ 100 years ago. A. was built​B. builds​C. has been built​D. built 8. Unless we can find new sources of energy, our life will certainly _______. A. affected​B. be affecting​C. affect​D. be affected 9. A lot of inventions _______ to serve human life A. have done​B. has made​C. have to do​D. have been made 10. Computers ______ since 1940s. A. is in used​B. was used to​C. used​D. have been in used 11. It is believed ______. A. that Alice is a talented ballet dancer​​ B. how is Alice a talented ballet dancer C. why is Alice such a talented ballet dancer​ D. when Alice to become a talented ballet dancer 12. Mr.Pike _____ the most famous archaeologist in our city. A. says to be​​B. is said to be​​C. is said that​​D. said to be 13. Thousands of people are reported _______. A. having lost their homes after the flood​​B. to have lost their homes after the flood C. to having lost their homes after the flood​​D. that have lost their homes after the flood 14. The factory is said ______ in a fire two years ago. A. being destroyed​​​​​B. to destroy​​​ C. to have destroyed​​​​​D. to have been destroyed 15. _____ that the kidnappers asked for one million dollars. A. It reports​​​​​​​B. It is reporting​​ C. It was reporting​​​​​​D. It was reported 1. ______ so upset! ​A. Has the boss seldom been​B. Seldom the boss has been ​C. Seldom has the boss been​D. Has the boss been seldom 2. ______ us to have private talks in class. ​A. At no time does our teacher allow​B. At no time our teacher allows ​C. At any time does our teacher allow​D. At any time our teacher allows 3. ______ the clothes since her husband bought a washing machine. ​A. Any longer she has washed​B. Any longer has she washed ​C. No longer she has washed​D. No longer has she washed 4. ______ what surprises we have in store for her. ​A. Little she knows​​B. Does she little know​ ​C. Does she know little​​D. Little does she know 5. ______ seen such awful behavior. ​A. Have I never before​​B. Before have I never ​ ​C. Never before I have​​D. Never before have I 6. ______ us an apology. ​A. Not once the manager offered​B. Not once did the manager offer ​C. Did the manager not once offer​D. Didn’t once the manager offer 7. Under no circumstances ______ to open the door themselves. ​A. passengers permit​​B. do passengers permit ​C. passengers are permitted​D. are passengers permitted 8. Only by working hard ______ good marks in the final exam. ​A. we get​B. we can get​C. can we get ​D. do we get 9. In no circumstances ______ on campus.​​ ​A. smoking should be allowed​B. should allow smoking ​C. we should allow smoking​D. should smoking be allowed 10. ______ such a talented singer. ​A. Have we enjoyed seldom​B. Seldom we have enjoyed ​C. Seldom have we enjoyed​D. Have we seldom enjoyed 11. Only after you obtain a driving license, _______ a car. A. you are able to drive ​​​B. can you drive C. you will be able to drive ​​ D. did you drive 12. Hardly ever _______ far from home. A. she traveled ​ B. she has traveled ​​C. did she travel D. she did travel 13. Had they arrived at the fair earlier, they _______ what they wanted. A. had found ​ B. have found ​​ C. found D. would have found 14. Only by working hard _______ your final exam. A. will you pass ​B. you will pass ​​C. did you pass D. you passed 15. Only when I have free time _______ television. A. I watch ​​B. will I watch ​​C. do I watch D. I watched