Walkabout wrote:
Attachment:
volume.png
In the rectangular solid above, the three sides shown have areas 12, 15, and 20, respectively. What is the volume of the solid?
(A) 60
(B) 120
(C) 450
(D) 1,800
(E) 3,600
We are given a rectangular solid and also are given areas of three of the sides. Let’s draw the figure out. We label the length, width, and height. We also label each side as side A, side B, and side C.
We see that the area of side A is length times height, that of side B is length times width, and that of side C is height times width.
We are given that the sides have areas of 12, 15, and 20.
Let’s say:
Side A area = 20Thus we can set up the following equation for area:
length x height = 20
Side B area = 15Thus we can set up the following equation for area:
length x width = 15
Side C area = 12height x width = 12
Analyzing the two equations, length x height = 20 and length x width = 15, we see that both 15 and 20 are multiples of 5 and we also see that each equation contains the common term of “length”. Thus, we can deduce that the length could equal 5. When length is 5, we see height is 4, and when length is 5, we see that width is 3. We now have our dimensions for length, width, and height.
length = 5
width = 4
height = 3
Since volume of a rectangular solid = length x width x height, the volume is:
5 x 4 x 3 = 60.
The answer is A.
(Note: If we were struggling to know which side, was side A, B, and C, we could have selected those sides in any order and we would have ended up with the same value for the volume. If that were not the case, we would have to have been given more specific instructions about which sides corresponded to which areas.)
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