Question

130. The traffic lights at three different signal points
change after every 45 seconds, 75 seconds and 90
seconds respectively. If all change simultaneously
at 7 : 20 : 15 hours, then they will change again
simultaneously at
[CLAT, 2016]
(a) 7:28: 00 hours (b) 7:27 : 45 hours
(c) 7 : 27 : 30 hours (d) 7 : 27 : 50 hours​

Answer 1

Answer:

Step-by-step explanation:

if they change after every 45, 75 and 90 sec respectively then we will find the lcm as lcm is the least value in which they will meet

therefore by finding the value 45 , 75 and 90 we get

now note 450 is seconds so we add 450 sec to the present time

which is 7×60+30 sec = 7min 30sec or 7:27:45 hours