Lights set

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Lights set

by jessicamuniz » Sun Oct 26, 2008 8:55 am
Here is another one (at last but not ar least)...

Three utility lights are set on timers. The first flashes every 15 seconds, the second flashes every 17 seconds, and the third flashes every 20 seconds. If, at given moment, the three lights flashs at exactly the same time, how many seconds will elpase before the next such ocurrance=
a. 30
b. 255
c. 510
d. 1,020
e. 5,100

Thanksin advance
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by vishubn » Sun Oct 26, 2008 9:02 am
is the answer 1020 !!

I mean LCM of 15,17,20 is 1020 seconds !

i.e.

5*3*4*17=1020

so it will take 1020 seconds for such occurance

vishu

OA??

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by rohangupta83 » Sun Oct 26, 2008 9:21 am
it should be 1020

15,17 and 20 are all factors of 1020

imo D