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Q.

A red light flashes 3 times per minute and a green light flashes 5 times in two minutes at regular intervals. If both lights start flashing at the same time, how many times do they flash together in each hour?

 A.

30

 B.

29

 C.

31

 D.

32

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Solution:
Option(A) is correct

Red light flashes every 20 seconds

Green light flashes every 24 seconds

Therefore, they will flash together every 120 seconds

In every hour, they will flash = \(\dfrac{3600}{120}=30\) times

Edit: Thank you, Dan, for notifying the typo, corrected it.


(4) Comment(s)


Harshit Varshney
 ()

Red light - 3 times--1 min

6times --2min

green light- 5 times--2min

red light -150 times-- 60 min

green light -180 times-- 60 min

now take the HCF (150,180)=30



Sm Mudabbir
 ()

red light will flash 6 times in 2 minutes and green flash 5 time in 2 min their lcm is 30 that is it



Dan
 ()

Please correct the answer . It will be unitless as it is asked how many times lights will flash in 1 hour.


Deepak
 ()

Thank you, Dan, for notifying, corrected it.