Jump to content
BrainDen.com - Brain Teasers

Rob_Gandy

Members
 View Profile  See their activity

  • Posts

    175

  • Joined

  • Last visited

  • Days Won

    2

 Content Type 

Posts posted by Rob_Gandy

  1. Stopping and Turning back hands of time

    in New Logic/Math Puzzles

    Posted

    @captainEd, the pic is not the start, both @ 12 o'clock is the start where the hands are moving clockwise, eventually the MH overtakes the HH causing it to stop but the MH keeps going until it reached the stopped HH again where then it reverses its direction (like bumping) while causing the HH to move again(resume running clockwise) . No double interpretations is intended here.

    From the last part where the MH 'bumps' the HH making it move again. The MH travels CCW until it hits the HM again making it stop then makes a full revolution CCW till it 'bumps' the HH which starts moving again and the MH begins traveling CW?

    There's more than meets the eye here.

    I've gone back and forth and concluded a couple things.

    The answer is not simply 23 hours.

    The answer might be "a very long time, if ever."

    I have some more work to do on this answer.

    It's a very nice puzzle.

    I agree now that I understand the OP a little more.

    the answer will be a whole number of hours. The real problem is to find out how many times the HH stops which is the number of extra hours the MH goes around the clock.

  4. where's the plane?

    in New Logic/Math Puzzles

    Posted · Edited by Rob_Gandy

    No clue about how to come up with a formula, but I did draw it out.

    there are two answers.

    post-52706-0-55636500-1361474000_thumb.j

    1) I constructed the triangle KJB with the scale 1cm=1000ft.

    2) I constructed two circles circle M and circle J with radii of 2.2cm and 7.7cm respectively.

    3) The intersections of these two circles (points A and B) indicate where the sound 'is' when Kiru hears it or the locations that are 2.2 secs from Michelle and 7.7 secs from John.

    4) Now the sound must originate from a point equidistant from K and A or K and B in other words on the perpendicular bisector of KA or KB.

    5) I constructed KA, KB and their perpendicular bisectors (CD and EF) and marked the midpoints of KA and KB (M and N).

    Now lets look at the point of origin associated with KA and its perpendicular bisector. (The other went off the page)

    6) I constructed ray MA and ray JA by extending the radii of the two circles from 2).

    7) Ray MA intersects CD at G and ray JA intersects CD at H.

    8) I constructed the angle bisector of angle GAH (ray AL).

    9) Ray AL intersects CD at O which should be one possible point of origin for the sonic boom.

    If I had a larger sheet of paper steps 6-9 could be repeated to find the other point.

    I didn't really think about the height of the plane though....oops

    Edit:bad tags

  18. Can you find a closed form equation for the sequence?

    in New Logic/Math Puzzles

    Posted

    This problem recently popped back into my head. In one of my college calculus classes while working on sequences we came across the sequence 0,0,1,1,2,2,3,3,4,4,... and if I remember correctly we were told there was no closed form equation for it. But, I found one and presented it to the class.

    a[n]=(2n-1+(-1)n)/4 n=0...infinity

    My question is: Is there a closed form equation to define the sequence 0,0,0,1,1,1,2,2,2,3,3,3....? If not, why not?

    Just wondering. :D

×
×
  • Create New...