Có 3 cái chuông trong phòng thí nghiệm. Chuông thứ nhất cứ 8 phút reo một lần. Chuông thứ 2 cứ 12 phút reo một lần. Chuông thứ 3 cứ 16 phút reo một lần.Cả 3 cái chuông cùng reo 7 giờ 30 phút sáng. a) Hỏi 3 chuông lại cùng reo lần tiếp theo vào lúc nào ? b)Hỏi trong khoảng từ 7 giờ 30 phút đến 11 giờ 30 phút có bao nhiêu lần nghe thấy tiếng chuông đồng thời của chỉ 2 trong 3 chuồng.

Các câu hỏi liên quan

1. (I / wake up late / I / be late for work) _______________________________________________________________ 2. (my husband / cook / he / burn the food) _______________________________________________________________ 3. (Julie / not wear a hat / she / get sunstroke) _______________________________________________________________ 4. (children / not eat well / they / not be healthy) _______________________________________________________________ 5. (you / mix water and electricity / you / get a shock) _______________________________________________________________ 6. (people / eat / too many sweets / they / get fat) _______________________________________________________________ 7. (you / smoke / you / get yellow fingers) _______________________________________________________________ 8. (children / play outside / they / not get overweight) _______________________________________________________________ 9. (you / heat ice / it / melt) _______________________________________________________________ 10. (I / speak to John / he / get annoyed) _______________________________________________________________ May be freely copied for personal or classroom use. 11. (I / feel good the next day / I / go to bed early) _______________________________________________________________ 12. (lots of people / come / Jenny / have a party) _______________________________________________________________ 13. (she / buy expensive clothes / she / go shopping) _______________________________________________________________ 14. (my daughter / pass her exams / she / work hard) _______________________________________________________________ 15. (David / be sick / he / drink milk) _______________________________________________________________ 16. (the river / freeze / it / be very cold) _______________________________________________________________ 17. (I / like to visit the museums / I / be in a new city) _______________________________________________________________ 18. (I / cycle to work / the weather / be fine) _______________________________________________________________ 19. (my flatmate / clean it really well / she / clean the house) _______________________________________________________________ 20. (everybody / be grumpy / it / rain a lot) ___________________________________