15. Three mark example problems III

There are four mobile phones in a house. At \(5\). a.m, all the four mobile phones will ring together. Thereafter, the first one rings every \(15\) minutes, the second one rings every \(20\) minutes, the third one rings every \(25\) minutes and the fourth one rings every \(30\) minutes. At what time, will the four mobile phones ring together again?

 

 

The four mobile phones will ring together at 10:00 a.m5:00 a.m5:00 p.m10:00 p.m.