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Finding area

  • 11-08-2009 12:08pm
    #1
    Nerin
    Registered Users, Registered Users 2 Posts: 10,523 ✭✭✭✭


    a bag of stones is .85metres in length each side of the bag. The bag is a cube shape.

    How do you calculate how much the bag will roughly cover?


Comments

  • #2
    Fremen
    Registered Users, Registered Users 2 Posts: 2,481 ✭✭✭Fremen


    You know how to get the area of a square once you know its side length, right?

    Once you have that, just multiply by the number of faces on a cube.

    Edit: after reading Yakuza's post, maybe I should clarify. I assumed you were trying to find the surface area of the bag.


  • #3
    Yakuza
    Registered Users, Registered Users 2 Posts: 5,141 ✭✭✭Yakuza


    The volume of the bag is (.85m)³, or 0.614125 m³.

    However, I think you're trying to find out what area that the stones in the bag will cover, and for that we need more information...the average volume of a stone for one thing, or its average height, width and depth (or radius if you want to approximate the stones as spheres).

    Once the volume of stones in the bag is known, then you can calculate the number of stones in the bag, and also can deduce how much area it will cover.


  • #4
    Nerin
    Registered Users, Registered Users 2 Posts: 10,523 ✭✭✭✭Nerin


    Woah,thanks for the quick replies. We were just disagreeing in work so we put ourselves in doubt of eachother :p

    We were looking for a very rough way to see what one bag would cover.
    We got the volume as .6 and the boss reckons finding the area the customer wants covered(for example 5x5 metres) then dividing it by the .6 bag would do it. I'm not so sure.


  • #5
    Yakuza
    Registered Users, Registered Users 2 Posts: 5,141 ✭✭✭Yakuza


    Let me give you an example to clarify:
    Assuming that the stones are smallish stones of (say) 2cm in diameter, then in a bag that was .85 * .85 * .85 m you would be able to cover 42 * (.85 *.85) m², or in this case 30.345 m² (or roughly 5m * 6m).

    Thinking of the bag as a cube, the area of the bottom face as a layer of cubes that is (0.85 *0.85) m² or 0.7225m². You would have enough pebbles for 42 such layers (85cm / 2cm, rounded down) hence the 30-odd m².

    If the stones are bigger or smaller, you would need to adjust your calcs accordingly

    Your boss is dividing an area by a volume which will give you the number of layers that you need, but you will still need the average dimensions / volume of a stone to calc the area it will cover; you could have one boulder of .85 * .85 * .85 m which isn't going to cover much :)

    I hope that helps.


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