Question

Liev is assembling a coffee table. The diagram below is from the instruction manual and shows the table after the first two legs have been attached.
Note: Figure is not drawn to scale.
The next step in assembling the coffee table is to attach support from point D to point C, which is halfway down leg A

The table legs are each 18 inches tall. What is the length of the support?

Answer 1

Answer:

The support is 41 inches long.

Step-by-step explanation:

There's two ways we can do this: one with the diagonal formula and one without.

Since we know that Point C is halfway down leg A and that the table legs are 18 inches tall, Point C is 9 inches down leg A. The support, from Point C to Point D, will form a diagonal, the length of which we need to find. We know from the diagram that the width of the table is 24 inches and that its length is 32 inches. We have a height, length, and width for this problem, so let's imagine a rectangular prism, which has all three of those things, instead of a table. The formula for finding a rectangular prism's diagonal is $d = \sqrt{l^{2} + w^{2} + h^{2} }$. Let's put in those numbers:

$d = \sqrt{32^{2} + 24^{2} + 9^{2} } = 41$

Therefore, the support is 41 inches long.

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Another way you can do this is to use the Pythagorean Theorem twice: once to find the diagonal of the tabletop and another time for the support.

$24^{2} + 32^{2} = c^{2} \\576 + 1024 = c^2\\1600 = c^2\\\sqrt{1600} = \sqrt{c^2}\\ 40 = c$

Now that we know the corner-to-corner distance for the tabletop, we'll use that and the 9 inch distance for Point C to find the distance between C and D:

$9^{2} + 40^{2} = c^{2}\\ 81 + 1600 = c^2\\1681 = c^2\\\\sqrt{1681} = \sqrt{c^2} \\41 = c$

Again, the support is 41 inches long.