beep , beep!

Calculus Level pending

Four different electronic devices make a beep after every 30 minutes , 1 hour , 1&1/2 hour and 1 hour 45 minutes respectively . All the devices beeped together at 12 noon . They will again beep together at ?

Note: No need to give a.m or p.m


The answer is 9.

A Former Brilliant Member by A Former Brilliant Member

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4 solutions

Achal Jain
Mar 24, 2017

Why Calculus?? \textit {Why Calculus??}

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Parag Zode
Jul 21, 2014

First convert the time into minutes i.e 30 min , 60 min , 90 mins and 105 mins respectively , say.. LCM of 30 ,60 ,90 ,105 is 1260 so 1260 min =21 hours. so, after 21 hours all devices will beep together i.e at 9 AM

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Guiseppi Butel
Jun 26, 2014

The LCM of those numbers is 21 which added to 12 noon gives 9 AM

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Dipesh Bhandari
May 27, 2014

Beeps together again at 9

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