A four inch thick concrete slab i sbeing poured for a circular patio ten ft in diameter.?

A four inch thick concrete slab is being poured for a circular patio ten feet in diameter. Concrete costs $50 per cubic yard. Find the cost of the concrete, to the nearest cent. Help, my answer seems way off, thanks! I got the same answer Rich so I guess I did it right, thanks!

4 Comments on “A four inch thick concrete slab i sbeing poured for a circular patio ten ft in diameter.?

  1. 10ft = 10/3 yards

    4inch = 4/ thirty six yards

    volume of concrete required = depth*pi*D^2 where D = diameter

    pi * (4/36)*(10/3)*(10/3) = 100pi/81 = 3.879 cubic yards

    cost = 3.879 * fifty =$193.925

  2. Area of a circle = pi * r^2
    r = d/2 = 10ft/2 = 5ft
    A = pi * 5^2 = 78.54 ft^2
    Volume = Area * depth
    Vol = 78.54 ft^2 * 4in * 1ft/12in = 26.18 ft^3
    1 yd^3 = twenty seven ft^3
    $50/27ft^3 * 26.18ft^3 = $48.48

  3. You have a cylinder, radius ten feet, height four inches = 4/12 feet = 1/3 feet

    Volume = pi*r^2*h = 3.142 * ten * ten * (1/3) = 104.73 cu feet

    1 cubic yard = 3*3*3 cubic feet = twenty seven cubic feet

    So volume = 104.73/27 cubic yards = 3.9 cubic yards to one decimal place

  4. You are using the diameter of the circle instead of the radius. The area of a circle is pi r squared, not pi d squared.

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