Results 1 to 2 of 2

Math Help - If 2 cm thick glass blocks 40% of the light how much 1 cm thick blocks

  1. #1
    Newbie
    Joined
    Dec 2012
    From
    Europe
    Posts
    7

    If 2 cm thick glass blocks 40% of the light how much 1 cm thick blocks

    This is such a stupid problem, but my brain is completely locked when I try to figure out the rationale for why it is A or B. A it is 20%, because 1 cm is 50% of 2 cm and 20% is 50% of 40%. or B it is 1-0.6^0.5=0.22.. ~22% because the 2 cm thick lets 60% in and the 1 cm is half of it, so that type of equation would seem to make some sense.

    Thanks for the help.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    Joined
    Sep 2012
    From
    Australia
    Posts
    3,607
    Thanks
    591

    Re: If 2 cm thick glass blocks 40% of the light how much 1 cm thick blocks

    Hey ManIsuck.

    It depends on how it blocks the light.

    I'm going to assume that each individual slab blocks a specific percentage of light coming in.

    In this case 2cm blocks 40% of the light which means 60% gets in.

    This means that it blocks 1 - r - (1-r)r = 0.6 or 1 - r - r + r^2 = 0.6. I am blocking for the first 1cm slab and then I'm taking that result and blocking it again.

    In this case we get 1 - 2r + r^2 = 0.6 so this leaves (1-r)^2 = 0.6 or 1-r = SQRT(0.6) or r = 1 - SQRT(0.6) since r < 1.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Hello! - I am thick....
    Posted in the Math Topics Forum
    Replies: 4
    Last Post: August 21st 2012, 07:25 AM
  2. Random blocks that fit together
    Posted in the Geometry Forum
    Replies: 0
    Last Post: September 18th 2011, 10:11 AM
  3. Is this set thick in C0
    Posted in the Differential Geometry Forum
    Replies: 2
    Last Post: March 7th 2010, 08:45 PM
  4. thick wall cylinders
    Posted in the Advanced Applied Math Forum
    Replies: 0
    Last Post: November 27th 2009, 07:59 AM
  5. [SOLVED] Too thick to solve this problem!!!!
    Posted in the Algebra Forum
    Replies: 2
    Last Post: January 19th 2006, 02:14 PM

Search Tags


/mathhelpforum @mathhelpforum