Question

four bells ring at four intervals, viz 8 min, 20 min, 25 min, and 40 min.find the number of times they would ring together in 87 hours

Answer 1

LCM of 8, 20, 25, 40 is 200.
Therefore, they will ring together after an interval of 200 minutes.
∴ In 87 hours they will ring 87x60/200 = 26.1= 26 times and once at the start; so total = 26 + 1 = 27