Question

8. On Ashok Marg three consecutive traffic lights
change after 36, 42 and 72 seconds, respectively. If
the lights are first switched on at 9:00 A.M. sharp,
at what time will they change simultaneously?
(a) 9 : 08 : 04 (b) 9:08 : 24
(c) 9 : 08 : 44 (d) None of these

​

Answer 1

Lcm of 36,42,72=504

so after 504 seconds they will change simultaneously.

504 seconds =504/60=8mins 24 sec

So add 8 mins 24 sec to 9 am....

ans will be 9:08 :24

Answer 2

The correct option is B.

Step-by-step explanation:

It is given that on Ashok Marg three consecutive traffic lights change after 36, 42 and 72 seconds, respectively.

LCM of 36, 42 and 72 is 504.

It means after 504 seconds the lights change simultaneously.

60 seconds = 1 minute

Convert 504 seconds in minutes.

$\dfrac{504}{60}=8+\dfrac{24}{60}$

504 seconds = 8 minutes 24 seconds.

The lights are first switched on at 9:00 A.M.

$9:00:00+00:08:24=9:08:24$

Therefore, the correct option is B.

#Learn more

The traffic lights at three different road crossing change after 24 seconds, 30 seconds and 36 seconds respectively. If they change simultaneously at 8:00 a.m.,at what time will they change simultaneously again ?

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