Respuesta :
You can use the fact that the middle area can be found by subtracting internal area from the total area.
The amount of wood(in area, assuming almost flat) needed by the carpenter to build the frame is given by
Option A: 5.5π + 106 sq. inches.
How to get the area between two things?
The middle area can be found by subtracting internal area from the total area.
For example, if you've got a big circle, and a small circle inside that big circle, and you want the remaining area in the big circle not occupied by smaller circle, then we have
Remaining area = Area of bigger circle - Area of smaller circle
Using the above methodology to find the amount of wood needed by the carpenter to build the given frame
The diagram is attached below.
The wooden region between those two semicircles in the top is of this below area
Area of bigger semicircle - Area of smaller semicircle.
Since bigger semicircle has 6 inch radius and smaller has 1 inch less(since width of the wood is 1 inch everywhere) which is 5 inch radius, thus,
As area of semicircle with radius r units is [tex]\dfrac{\pi r^2}{2} \: \rm unit^2[/tex]
Thus,
Area of wood between two semicircles = [tex]\pi \times 6^2/2 - \pi \times 5^2/2 = \pi \times 11/2 = 5.5\pi \rm \: \: inch^2[/tex]
Area of the wood in the bottom of the window = area of rectangle GLMH
Since |GL| = |HM| = 1 inch and |LM| = 12 inches, thus, as
Area of rectangle = length times width
thus,
Area of GLMH = [tex]1 \times 12 = 12 \rm \: inch^2[/tex]
Remaining wood is as rectangle ABGE and CDFH
- Area of ABGE wood
Since we have |AL| = 48 inches but |GL| = 1 inch, thus, |AG| = 47 inches(1 less than |AL|
Also, since |GE| = 1 inch wide, thus,
Area ABGE = [tex]1 \times 47 = 47 \: \rm inch^2[/tex]
- Area of CDFH wood
Similar to above case, we have
Since we have |DM| = 48 inches but |HM| = 1 inch, thus, |DH| = 47 inches(1 less than |DM|
Also, since |FH| = 1 inch wide, thus,
Area CDFH = [tex]1 \times 47 = 47 \: \rm inch^2[/tex]
Thus, total wood used(in terms of area) = Area CDFG + Area ABCD + Area of bottom rectangle GLHM + Area of the internal of two semicircles on top ADCB(thick arc like shape)
or
Total area of wood = 47 + 47 + 12 + 5.5π = 5.5π + 106 sq. inches.
Thus,
The amount of wood(in area, assuming almost flat) needed by the carpenter to build the frame is given by
Option A: 5.5π + 106 sq. inches.
Learn more about area of semicircle here:
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