NC42003
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You built a coffee table for your living room. The next step, before you put it together, is to stain it. How much wood stain should you buy to cover the entire table? Find the surface area to find the amount of stain needed. Use 3.14 to approximate pi.

You built a coffee table for your living room The next step before you put it together is to stain it How much wood stain should you buy to cover the entire tab class=

Respuesta :

AL2006
Wow.  This is complicated.  It's not hard ... it just has a lot of steps to it.

-- The top, round surface, where the cups and glasses sit:

A circle.  The area of a circle is    (pi) (radius)²
                                                     = (3.14) (24 inches)²
                                                     = (3.14) (576 square inches)
                                                     =      1,808.64 square inches

-- The 8-inch edge around the table-top.
    This is actually a long skinny rectangle, wrapped around it.
    The width of the rectangle is 8 inches.
    The length of the rectangle is the circumference of the table-top.

Circumference of a circle = (pi) (diameter)
                                           = (pi) (2 x radius)
                                           = (3.14) (48 inches)
                                           =      150.72 inches

Area of the long skinny rectangle = (8 inches) x (150.72 inches)
                                                        =     1,205.76 square inches .

-- Legs.
   Each leg is a rectangular prism.
   Area of the bottom of the leg, where it stands on the floor
                                 = (2.5 inches) x (2.5 inches) = 6.25 square inches
   Area of each of the 4 sides =
                                 = (10 inches) x (2.5 inches) = 25 square inches
   Area of the top of the leg:  glued to the table-top; not stained.
   Total surface area of each leg = (6.25 + 25) = 31.25 square inches)

   Surface area of all 4 legs = (4) x (31.25) = 125 square inches.

So far, we have:
-- table-top . . . . . . . . . . . .  1,808.64 square inches
-- strip around table-top . . 1,205.76 square inches
-- 4 legs . . . . . . . . . . . . . . .    125      square inches
                   Total                 3,139.4 square inches

This is not one of the choices.
Did I miss something ?
What about the underside of the tabletop ?

That's                (the same area as the top of the table-top)
               minus
                         (the 4 little squares where the legs are glued on) .

Let's try that.

Area of the full round surface of the table-top = 1,808.64 square inches

... Each little square
    where a leg is glued on = (2.5 x 2.5) = 6.25 sq inches.
    Four of them = (4 x 6.25)  =                                         25 square inches

Area of the part of the underside that needs to be stained =

                                 (1,808.64 - 25)  =  1,783.64 square inches

So now we have:
-- top surface of the table-top. . . . .  1,808.64 square inches
-- strip around table-top . . . . . . . . . . 1,205.76 square inches
-- bottom surface of the table-top . . 1,783.64 square inches
-- 4 legs. . . . . . . . . . . . . . . . . . . . . . .    125       square inches

                                       Total:            4,923.04 square inches

At this point, I'm going to pull a fast one on you, and talk to you
like the Engineer that I am.  You might not like it.

This answer that I have is not exactly the same as any of the choices.
But it's only 12.5 square inches (0.25%) less than one of them.
So now I'm going to say:

-- the choice of 4,935.54 must be the correct one;
-- I must have made a small arithmetic error somewhere, but
I believe I worked the problem correctly; and
-- I've already spent enough time on this one to earn 5 points,
and I'm not going to spend any more of it.

The correct answer according to your ttm would be exactly 5,273.04 square inches all of the other answers are wrong. I guarantee this is correct. :)