Question

The traffic lights at three different road crossings change after every 48 seconds, 72

seconds and 108 seconds respectively. If they change simultaneously at
7 a.m., at what time will they change simultaneously again?

please tell step by step​

Answer 1

7 : 7 : 12 am

Explanation:

This question pretty much requires us to obtain the lowest number that is common to all three times. The qay to obtain this is by finding the LCM of all three numbers.

This is given as;

48 = 2 × 2 × 2 × 2 × 3

72 = 2 × 2 × 2 × 3 × 3

108 = 2 × 2 × 3 × 3 × 3

The LCM is = 2 × 2 × 2 × 2 × 3 × 3 × 3 = 432 seconds.

Converting to minutes by dividing by 60, the time is = 432 ÷ 60 min = 7 min 12 sec

The next time they would change simultaneously is; 7am + 7 min 12 sec = 7 : 7 : 12 am