21not 12:30 , at 12:32 or 33 , something like that
this i believe was given by a friend of einstien to him, when he was ill, wounded and bed ridden in a hospital, to indimidate him, instead, einstien, though not completely conscious, solved it orally, much to the friends disappointment :P , so much for the history,
How many times in a day do the minute and hour hands of a mechanical clock come to be exactly anti-parallel, (ie 180 degrees between them)? not unsolvable, try it out.
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23 Answers
112 times in a day the hour hand and the minute hand are anti-parallel
106first time after 12:00 that they become antiparallel
ang speed of hr hand = 360°/(12hr) (asssuming 12 hr clock)
ang speed of min hand = 360°/(1hr)
relative ang. speed = 360°12hr*11
so relative angle = 180°
so time = 180°/ωrel = 12hr*180°360°*11 = 12/22 hr = 6/11 hr
So, the time just after 12:00 when hands at 180° are = 12+6/11 hr
62A simple hint:
Think of 30 days of a month...
every one will agree that the answer will be 24x28+ additional 24x2 or 23x2
If you take 365 days... 24x365 approx
SO as you keep increasing the number of days the answer comes to 24
I am not saying that this is the proof... I am sure some of you can try to find the times at which this happens..
Can someone try to find the exact time that it happens for the first time after 12:00?
1hey dude see it again ur list contains 23 times nd 12:35 is included 3 times so it also make it to 22 times na............:P:)
1i guess like this (" I am takin approximate times here...")
12 : 35
1 : 39
2 : 43
3: 50
4 : 55
6: 00
7 : 05
8 : 10
9 : 15
10 : 20
11 : 25
12 : 35
1 : 39
2 : 43
3: 50
4 : 55
6: 00
7 : 05
8 : 10
9 : 15
10 : 20
11 : 25
12 : 35
Altogether 24 times in a day :)
1Agreed with Jai Hind.
At 12:30 the hands are not exactly antiparallel.
1well ya...solving it orally (with about 10-15 seconds of thinking), i think it shud be 24...they will be antiparallel exactly once each hour...
1i thought this cozz der r gaps b/w two consecuttive no.'s nd with every gap der is one relation (b/w min nd hr of clock) is associatednd der r 11 gaps in 12hrss.......soo total 22 gaps in 24 hrss.i hope u understand ma sol.n nd the gaps i mean ..........
1HEY SANCHIT YAAR...DONT MIND...DIMAAG PE JOR LAGAO!!! MIN ITS 24 YAAR....
