Results 1 to 9 of 9

Math Help - Need to find the density

  1. #1
    Newbie
    Joined
    Sep 2008
    From
    Norfolk, UK
    Posts
    16

    Exclamation Need to find the density

    Volume = 2.00 ft3 Mass = 97.5 lb Density = ? g/cm3

    Can someone work this out for me please?

    I am working on an example in a book and I cant seem to get the same answer.

    Wondering if the book has a missprint (its probably just me though )

    Thanks

    $ilver
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Super Member
    Joined
    Jun 2008
    Posts
    792
    You need to find the density in g/cm^3. First convert mass from lb to g and volume from ft^3 to cm^3. Recall that:

    1~\text{ft} = 30.48~\text{cm} \implies 1~\text{ft}^3 = (30.48)^3~\text{cm}^3

    1~\text{lb} = 453.6~\text{g}

    Then find the density \rho = \frac{m}{V}.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Sep 2008
    From
    Norfolk, UK
    Posts
    16
    Well the answer in the book says Density = 0.780896 = 0.781 g/cm3

    But I dont get that answer, I get 0.195

    Follow Math Help Forum on Facebook and Google+

  4. #4
    Super Member
    Joined
    Jun 2008
    Posts
    792
    The book's answer is correct. Post your work here and I (or someone else) will point out your mistake.
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Newbie
    Joined
    Sep 2008
    From
    Norfolk, UK
    Posts
    16
    Ok thanks for that Chop Suey much appreciated, will be a few hours till I can post because I am at work atm (boss keeps walking past lol)
    Follow Math Help Forum on Facebook and Google+

  6. #6
    Newbie
    Joined
    Sep 2008
    From
    Norfolk, UK
    Posts
    16
    Ok this is how I tried to work it out

    1ft = 30.48 cm x3 (because its cubed?) then x2 (the volume is 2.00 ft3) = 365.76 cm3

    1 lb = 453.6g so 453.6 x 97.5 = 44226g

    Then divide mass 44226g by volume 365.76cm =120.9153543
    Follow Math Help Forum on Facebook and Google+

  7. #7
    Super Member
    Joined
    Jun 2008
    Posts
    792
    Okay, it seems you are not familiar with exponents.

    When I said (30.48)^3, I meant 30.48 \times 30.48 \times 30.48.

    5^2 = 5 \times 5 = 25

    3^4 = 3 \times 3 \times 3 \times 3 = 81

    9^2 = 9 \times 9 = 81

    a^n = \underbrace{a \times a \times a \times \ldots \times a}_{\text{n times}}
    Follow Math Help Forum on Facebook and Google+

  8. #8
    Newbie
    Joined
    Sep 2008
    From
    Norfolk, UK
    Posts
    16
    Could you post the steps needed with the answers so I can see what I am doing wrong?

    Thanks

    $ilver
    Follow Math Help Forum on Facebook and Google+

  9. #9
    Newbie
    Joined
    Sep 2008
    From
    Norfolk, UK
    Posts
    16

    Thumbs up

    Ok no need I finaly got it.

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

Similar Math Help Forum Discussions

  1. Replies: 2
    Last Post: November 11th 2011, 05:06 AM
  2. help on to find probability density function!!!
    Posted in the Advanced Statistics Forum
    Replies: 3
    Last Post: July 2nd 2011, 10:46 PM
  3. Find mass by linear density?
    Posted in the Calculus Forum
    Replies: 9
    Last Post: July 13th 2010, 12:43 PM
  4. if X is uniform, find density function of Y=X^2
    Posted in the Advanced Statistics Forum
    Replies: 3
    Last Post: May 8th 2010, 02:36 PM
  5. Find the cumulative and probability density functions
    Posted in the Advanced Statistics Forum
    Replies: 3
    Last Post: March 24th 2010, 10:31 AM

Search Tags


/mathhelpforum @mathhelpforum