2023 · Q30
There are four bells which ring at an interval of 15 minutes, 25 minutes, 35 minutes and 45 minutes respectively. If all of them ring at 9 A.M., how many more times will they ring together in the next 72 hours?
Elementary MathematicsHCF and LCM
- A0
- B1
- C2
- D3
Explanation
The bells ring together every lcm(15, 25, 35, 45) = 1575 minutes = 26.25 hours. Starting from 9 A.M., they coincide again after 26.25 h and 52.5 h — both within the next 72 hours. So they ring together 2 more times (C).