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Tick Tock Bad Clock

Math brain teasers require computations to solve.

 

Puzzle ID:#49380
Fun:*** (2.75)
Difficulty:** (2.02)
Category:Math
Submitted By:firefox99tus******
Corrected By:FatHead

 

 

 



Your friend gave you a clock for your birthday, but unfortunately, it's very unreliable. This one gains exactly 12 minutes every hour.

It is now showing 10pm and you know that it was correct at midnight, when you set it.

If the clock stopped four hours ago, what is the correct time now?

Open Calculator

Answer

Since the clock gains 12 minutes every hour, for every real hour that has passed 72 minutes will pass on the clock. It has been 22 fake hours from midnight to the time the clock stopped, so in order to find the number of real hours we must first find the number of fake minutes, then divide the number of fake minutes by the number of minutes that pass by in an hour for the clock (72) to find the number of real hours that have passed from midnight to when the clock stopped. The following shows arithmetic work:

22 x 60 = 1320 (clock minutes that have passed from midnight to when the clock stopped)
1320 / 72 = 18.333333... (real hours that have passed from midnight to when the clock stopped)
18.333333... hours = 18 hours 20 minutes. Therefore it was 6:20pm when the clock stopped. And because the clock stopped four hours ago, it is now 10:20pm!

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Comments

Babe*
Apr 25, 2012

No comments eh? No wonder, people do not want to go back to school! This is supposed to be a fun quiz, not school work. Enough already!!!
thedavincigameA*
Apr 25, 2012

For those looking for a non-mathematical number riddle instead of a complex one:

What number's
cone alone flour - call

??
HABS2933Aca*
Apr 25, 2012

While I don't care for the math based teasers, I know that there are a lot of people who do (otherwise they would not have it as a category). Many people like the "school work" teasers as there are also literature and science type teasers as well.
IT was however refreshing to see a brand new teaser (less than a month old) as teaser of the day, much more enjoyable than seeing a teaser that is 5+ years old, the author of which has not even been on the site for almost as long.
elentirAus*
Apr 25, 2012

I like these teasers! Although, I think this qualifies more as a Math category than Logic.
elentirAus*
Apr 25, 2012

@thedavincigame - four
elentirAus*
Apr 25, 2012

I meant one one four - or 114
bradon182001*us*
Apr 25, 2012

Math, definitely not my favorite but this was fun to work out. Good job.
charlottes-oddAen*
Apr 25, 2012

This reminded me of being back in school haha good puzzle though me likes however... the clock in the riddle lies
tripleteam5*
Apr 25, 2012

seems wrong. If clock SAYS 10pm that is when it stopped and you add time lost to that It would seem
luluw5*us*
Apr 25, 2012

I hate the math teasers! i don't wanna b learnin math!!!
dimaspace*
Jun 30, 2012

Wrong answer!
22 fake hours give us 12"22 equals 264 fake minutes - 4 hours and 24 min

So it was 22-4.24 equals 17.36

And plus 4 hours - 21.36 for now or 9.36 pm NOT 10.20 pm

Author multiplies 22 by 60 - wrong, he should multiply it by 72
SRB_1807Ain*
Jul 20, 2012

the answer is 9:36 p.m ...
Author's answer is wrong ...
Churang*
Jul 08, 2013

dont really understand th equestion
spikethru4*au*
Jul 09, 2013

dimaspace, the 22 fake hours already includes all the fake minutes. After one hour has passed from midnight, the clock shows 1:12.

If F is the fake time in hours and R the real time in hours, then F = R * (1 + 12/60). When the clock stopped, the fake time was 220, so at that point, R = 22 / 1.2 = 18.33, or 6:20pm. Four hours later, the real time is 10:20pm, as stated.
spikethru4*au*
Jul 09, 2013

Poxy emoticons. That should be 22 : 00 above.



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