Question

6. The traffic lights at three different road crossings change after every 48 seconds, 72
seconds and 108 seconds respectively. If they change simultaneously at
7am., at what time will they change simultaneously again?
103 litres 434 litres and 465 litres of diesel respectively. Find​

Answer 1

Given that traffic light at three different road crossing change after every 48 seconds,72 seconds and 108 seconds respectively.
So let us take the LCM of the given time that is 48 seconds, 72 seconds, 108 seconds
48 = 2 × 2 × 2 × 2 × 3
72 = 2 × 2 × 2 × 3 × 3
108 = 2 × 2 × 3 × 3 × 3
Hence LCM of 48, 72 and 108 is (2 × 2 × 2 × 2 × 3 × 3 × 3) = 432
So  after 432 seconds they will change simultaneously
We know that 60 seconds = 1 minute
so on dividing 432 / 60 we get 7 as quotient and 12 as reminder
Hence, 432 seconds = 7 min 12 seconds
Therefore the time is = 7 a.m. + 7 minutes 12 seconds
Hence the lights change simultaneously at = 7:07:12 a.m
Hope it helps you..