Question

The traffic lights at three different road
crossings change after every 48 seconds.
72 seconds and 108 seconds respectively.
If they all change simultaneously at 6:10:
00 hrs then they will again change
simultaneously at (Asst Grade II- KSEB-
2015)
​

Answer 1

Solution:

Given that , The traffic lights at three different road crossings change after every 48 seconds, 72 seconds and 108 seconds respectively.

So, We have to find the LCM of Given Numbers;

•°• 48 = 2⁴ x 3

72 = 2³ x 3²

108 = 2² x 3³

Common Factor From those Numbers :

LCM = 2⁴ x 3³

LCM = 16 x 27

= 432

Here, Convert 432 seconds to minutes :

432 seconds = 432 ÷ 60 mins

432 seconds = 7.2 mins

Therefore, { 7 mins 12 seconds }

Now, According to the Question's Statement!

Statement : If they all change simultaneously at 6:10:

If they all change simultaneously at 6:10:00 hrs then they will again change

Adding Obtained Time to Given Number (Time)

•°• 6 : 10 : 00 + 7 minutes 12 Seconds

↪ 6 : 17 : 12

Hence, If they all change simultaneously at 6:10:00 hrs then they will change at 6 : 17 : 12 hrs

Answer 2

Solution:

Given that , The traffic lights at three different road crossings change after every 48 seconds, 72 seconds and 108 seconds respectively.

LCM of 48 , 72 and 108 Given Below :

48 = 2⁴ x 3

72 = 2³ x 3²

108 = 2² x 3³

LCM = 2⁴ x 3³ = 432

Convert 432 seconds to minutes :

432 seconds = 432 ÷ 60 mins

432 seconds = 7.2 mins

7 mins 12 seconds

Now, According to the Question's Statement!

= 6 : 10 : 00 + 7 minutes 12 Seconds

= 6 : 10 : 00 + 7 minutes 12 Seconds = 6 : 17 : 12 { Answer }

Therefore, If they all change simultaneously at 6:10:00 hrs then they will change at 6 : 17 : 12 hrs