find 90 degree Angle in a Clock

rakeen · Unread post by **rakeen** » Sat Mar 12, 2011 4:56 pm

Q. How many times a clock can create 90 degre angles between the 'minute prick' and the 'hour prick' in a different time? (obviously in a day, that means in 24 hr)

Hasib · Unread post by **Hasib** » Sat Mar 12, 2011 7:43 pm

what is prick means?

Mehfuj Zahir · Unread post by **Mehfuj Zahir** » Sat Mar 12, 2011 10:31 pm

hour prick means ghorir kata

Mehfuj Zahir · Unread post by **Mehfuj Zahir** » Sat Mar 12, 2011 10:33 pm

ans is 22 times

Hasib · Unread post by **Hasib** » Sat Mar 12, 2011 10:52 pm

I dont think the ans is like so. Let it is 3 o'clock. Then u will find 2 time(approximately 3:15 and 3:45) so the ans is more than 22.

Mehfuj Zahir · Unread post by **Mehfuj Zahir** » Sun Mar 13, 2011 2:27 am

3:15 te hour prick $&minute prick 90 degree angle hoi na.
Ans is 22 think carefully

Hasib · Unread post by **Hasib** » Sun Mar 13, 2011 1:52 pm

i say approximately and Sorry, it would be 12:15 and 12:45 approximately

rakeen · Unread post by **rakeen** » Sun Mar 13, 2011 7:21 pm

mehfuz iz right. coz is minute prick moves 1 unit then hr prick moves 1/12 unit.

i found it on sc olym

tarek like math · Unread post by **tarek like math** » Sat Apr 30, 2011 3:16 am

my answer also $22$
let make an equation
start from 12'o clock. difference in d between h and m prick is 0 degree.
after 1hour 330 degree in clockwise. it will work as mod. after difference 360 degree it will round again.
difference d increase with time same relation as gravity increase with mass.
let calculate, in 60 minute d is 330 then in 1 minute d is 330/60=5.5
so now we calculate difference 360 means both prick in same position.
d=5.5 in minute=1 then d=1 in m=1/5.5 then d=360 in m=360/5.5=65.45minute
now if d=90 then m=90/5.5=16.36 and d=270(at 12:45) m=270/5.5=49.09.
twice in hour 12~01.
If it has any error or beauty to you then reply it.

Dipan · Unread post by **Dipan** » Tue May 03, 2011 11:47 pm

@Tarek... the last two lines is not so clear to me.

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