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Math Help - Need help please!

  1. #1
    Newbie
    Joined
    Aug 2013
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    Edmonton
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    Need help please!

    A tennis ball is dropped from a height of 20 m and bounces to 40% of its previous height on each bounce. The total vertical distance travelled is made up of the upward bounces and downward drops. What is the total vertical distance for the 6th time?

    How do I incorporate the upward bounces and downward drops into the formula:

    t1=20
    r = .4
    n= 6

    Sn=t1(r^n-1)/r-1
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  2. #2
    MHF Contributor
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    Re: Need help please!

    Hey smyatsallie.

    Try adding each in pairs.

    First you have 20 then 2*0.4*20 (up and down 1) then 2*0.4*0.4*20 (up and down 2) and keep going to the 6th up and down which is 2*0.4^6*20.

    Then you add all of these up to get your total vertical distance. See if you can calculate the distances for each of the up and down pairs and then add them all up along with the initial 20 m drop.
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  3. #3
    Super Member
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    Re: Need help please!

    Need help please!-19-aug-13-2.png
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