Question

Traffic lights at three different road crossing change after 48 sec,72sec and 108 sec respectively. At what time will they change together again if they change simultaneously at 7 A.M.? (with full statement ) plz ans fast

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
That is after 432 seconds they will change simultaneously
432 seconds = 7 min 12 seconds
Thus the traffic lights change simultaneously at 7:7:12 am

Answer 2

First find the Lcm of the given numbers

48 = 2 × 2 × 2 × 2 × 3
72 = 2 × 2 × 2 × 3 × 3
108 = 2 × 2 × 3 × 3 × 3

LCM of 48, 72 & 108 = (2 × 2 × 2 × 2 × 3 × 3 × 3)
 = 432

after 432 seconds they will change simultaneously
432 seconds = 432/60 = 7 min 12 seconds

Thus the traffic lights change simultaneously at 7:7:12 am