The traffic lights at three different road crossings change after every 60 sec, 90 sec. and 120 sec. if they all change simultaneously at 12:40:00 hrs, when will they change together again?
Answers
Step-by-step explanation:
As we know the LCM of 60 , 90 , and 120 is 10*5*2*2*3=360s
we do cross multiplication as to convert 360 s to min i.e.360*1/60= 6min
add 6min
we get 12:46:00 hrs
Answer:
The traffic lights will change simultaneously again at 12:46:00 hours.
Step-by-step explanation:
In order to calculate the time when the three traffic lights change together once again, we need to calculate the LCM of the time taken by each of them to change.
1st light changes after every 60 sec
2nd light changes after every 90 sec
3rd light changes after every 120 sec.
∴ We will take the Lowest Common Multiple (LCM) of 60,90, and 120
60= 2×3×5×2
90= 3×2×5×3
120=2×3×5×2×2
Clearly, the Lowest Common Multiple of 60,90, and 120 is 6.
∴ The three traffic lights will change simultaneously/together again at 12:40:00+00:06:00 hours
= 12:46:00 hours