Question

the traffic lights at three different road Crossings change after every 48seconds 72sec and108 respectively if they all change simultaneously 8:20:00 hrs then when will they can change the simultaneously at

Answer 1

Given that traffic light at three different road crossing change after every 48 seconds,72 seconds and 108 seconds respectively.
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 count 432 seconds from 8:20.
432 seconds equals 7 minutes 12 seconds.
8:20:00 + 0:07:12=8:27:12