A gym has 6 different bells for 6 different exercises which ring at the end of each exercise. The duration of the exercises are 40, 45, 50, 60, 75 and 125 seconds. If the bells ring together at 9 AM, then at what time next will they ring together?
A gym has 6 different bells for 6 different exercises which ring at the end of each exercise. The duration of the exercises are 40, 45, 50, 60, 75 and 125 seconds. If the bells ring together at 9 AM, then at what time next will they ring together? Correct Answer 11:30 AM
Given:
4 Bells ring after 40, 45, 50, 60, 75 and 125 seconds respectively
Concept used:
The lowest common multiple (LCM) concept is used because LCM would give us the time interval at which the four bells ring simultaneously.
Calculations:
According to the question, we have
40 = 2 × 2 × 2 × 5
45 = 3 × 3 × 5
50 = 2 × 5 × 5
60 = 2 × 2 × 3 × 5
75 = 3 × 5 × 5
125 = 5 × 5 × 5
⇒ LCM of (40, 45, 50, 60, 75,125) = 5 × 5 × 3 × 2 × 2 × 2 × 3 × 5
⇒ 9000
LCM of (40, 45, 50, 60, 75,125) = 9000
Thus, all bells ring after 9000 seconds = 9000/3600 hour
⇒ 5/2 hour
⇒ 2 hour 30 min
The time they ring together again = 9 am + 2h 30 min
⇒ 11:30 AM
∴ At 11:30 AM they will ring together again.