Answer:
1180 cm³
Step-by-step explanation:
You want the volume of a prism with an L-shaped base. It is 20 cm between bases. The outside dimensions of the L are 7 cm high by 11 cm wide; the inside dimensions are 3 cm high by 6 cm wide.
Volume formula
The formula for the volume of a prism is ...
V = Bh
where B is the area of the base, and h is the distance between them. We know h, but we need to find B.
Base area
The area of an L-shape is the area of the rectangle with the outside dimensions, less the area of the rectangle with the inside dimensions.
A = LW -lw
A = (11 cm)(7 cm) -(6 cm)(3 cm) = 77 cm² -18 cm² = 59 cm²
Volume
Using the above formula, the volume is ...
V = (59 cm²)(20 cm) = 1180 cm³
The volume of the prism is 1180 cubic centimeters.
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Additional comment
The dimensions of the inside of the L are found by subtracting the given width of the legs from the outside dimensions.
7 cm -4 cm = 3 cm . . . . inside height
11 cm -5 cm = 6 cm . . . . inside width
You can also find the area of the base by extending one or the other of the lines to divide it into two rectangles. Extending the vertical line makes the left rectangle 7 cm high by 5 cm wide. The right rectangle is 4 cm high by 6 cm wide. Then the area is 7·5 +4·6 = 35+24 = 59, as above.
