Posers and Puzzles

Posers and Puzzles

  1. Joined
    01 May '07
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    27311
    15 Jun '07 04:51
    A rubber ball dropped 80 feet rebounds on each bounce 3/5 of the height from which it fell. How far will it ravel before coming to rest?

    😀

    for all you smart fellers
  2. Joined
    28 Jan '06
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    23351
    15 Jun '07 05:381 edit
    320 feet?
  3. Subscriberhuckleberryhound
    Devout Agnostic.
    DZ-015
    Joined
    12 Oct '05
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    42038
    15 Jun '07 05:43
    It's a rubber ball, it won't ravel atall.


    unless ravel means something different where you come from. 😛
  4. Joined
    18 May '05
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    38549
    15 Jun '07 06:01
    Originally posted by Drew L
    A rubber ball dropped 80 feet rebounds on each bounce 3/5 of the height from which it fell. How far will it ravel before coming to rest?

    😀

    for all you smart fellers
    It wont "travel" as it was dropped from height, if it was dropped perfectly vertical, it will rest where it first bounced. (in theory!)

    😉
  5. Joined
    01 May '07
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    27311
    15 Jun '07 06:21
    Originally posted by smomofo
    320 feet?
    Horah!

    320 feet it is.
  6. Joined
    28 Jan '06
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    23351
    15 Jun '07 06:27
    Cool. I actually figured that out on my own! Thanks.
  7. Joined
    01 May '07
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    27311
    15 Jun '07 06:34
    Originally posted by smomofo
    Cool. I actually figured that out on my own! Thanks.
    yeah, it was on my pre-calculus final.

    A1 / 1 - r where A1 = initial drop and r = rate of rebound

    First find the height of the first rebound

    80 * (3/5) = 48

    Second Use the geometric infinite geometric convergent formula [ once for the drop and once for the rebound, drop is given, step one finds the rebound]

    80 / 1 -(3/5) = 80 / (2/5) = 80 * (5/2) = 200

    48 / 1 -(3/5) = 48 / (2/5) = 48 * (5/2) = 120

    Finally, add the two numbers together and there you have it.
  8. Joined
    28 Jan '06
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    23351
    15 Jun '07 06:40
    I couldn't remember that stuff, so I just added the first few terms of (0.6) + (0.6)^2 + (0.6)^3 + ... and saw that it was headed for 1.5 and went from there. Maybe not the way it's supposed to be done, but I bet I could have faked my way to a decent mark on that question.
  9. Joined
    01 May '07
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    27311
    15 Jun '07 06:41
    Originally posted by smomofo
    I couldn't remember that stuff, so I just added the first few terms of (0.6) + (0.6)^2 + (0.6)^3 + ... and saw that it was headed for 1.5 and went from there. Maybe not the way it's supposed to be done, but I bet I could have faked my way to a decent mark on that question.
    hahaha, I got that one right and pulled off an 83 on the exam
  10. Joined
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    23351
    15 Jun '07 06:56
    nice
  11. SubscriberPonderable
    chemist
    Linkenheim
    Joined
    22 Apr '05
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    531109
    15 Jun '07 06:58
    Originally posted by smomofo
    I couldn't remember that stuff, so I just added the first few terms of (0.6) + (0.6)^2 + (0.6)^3 + ... and saw that it was headed for 1.5 and went from there. Maybe not the way it's supposed to be done, but I bet I could have faked my way to a decent mark on that question.
    This is a correct approach, you just should show that the series converges.
  12. Joined
    01 May '07
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    27311
    15 Jun '07 07:03
    Find the sum of the first 25 even integers that are larger than 17
  13. Joined
    28 Jan '06
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    23351
    15 Jun '07 07:08
    930
  14. Joined
    01 May '07
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    27311
    15 Jun '07 07:10
    Originally posted by smomofo
    930
    lets see, lets see

    not what i got but i could be mistaken

    😕
  15. Standard membersonhouse
    Fast and Curious
    slatington, pa, usa
    Joined
    28 Dec '04
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    52874
    15 Jun '07 12:00
    Originally posted by Drew L
    lets see, lets see

    not what i got but i could be mistaken

    😕
    I got 1050. I did it in groups of 5, 18+20+22+24+26 and found each group starting with 110 sum going up by 50 so it was easy to truncate the series, 110+160+210+260+310= 1050
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