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In the picture below, polygon ABCD ~ polygon WXYZ. Solve for m.

A
13
D 10 C
12
B
W
24
Z 15 Y
m
X
m =

User Jolita
by
7.3k points

1 Answer

3 votes

Since polygon ABCD is similar to polygon WXYZ, the corresponding sides are proportional.

That means:

AB/WX = BC/XY = CD/YZ = AD/WZ

We can use this fact to set up the following equations:

AB/WX = 13/24

CD/YZ = 12/15 = 4/5

AD/WZ = 10/m

We are given that AB = 13 and WX = 24, so we can substitute those values in the first equation:

13/24 = BC/XY

We are also given that CD = 12 and YZ = 15, so we can substitute those values in the second equation:

4/5 = BC/XY

Since both equations equal BC/XY, we can set them equal to each other:

13/24 = 4/5

To solve for m, we can use the third equation:

10/m = AD/WZ

We know that AD = AB + BC = 13 + BC, and WZ = WX + XY = 24 + XY. Since BC/XY is the same in both polygons, we can use the results from our previous equations to find that BC/XY = 4/5.

So we have:

AD/WZ = (13 + BC)/(24 + XY) = (13 + (4/5)XY)/(24 + XY) = 10/m

Now we can solve for XY:

13 + (4/5)XY = (10/m)(24 + XY)

Multiplying both sides by m(24 + XY), we get:

13m(24 + XY)/5 + mXY(24 + XY) = 10(13m + 10XY)

Expanding and simplifying, we get:

312m/5 + 13mXY/5 + mXY^2 = 130m + 100XY

Rearranging and simplifying further, we get:

mXY^2 - 87mXY + 650m - 1560 = 0

We can use the quadratic formula to solve for XY:

XY = [87m ± sqrt((87m)^2 - 4(650m - 1560)m)] / 2m

Simplifying under the square root:

XY = [87m ± sqrt(7569m^2 - 2600m)] / 2m

XY = [87m ± sqrt(529m^2)] / 2m

XY = (87 ± 23m) / 2

Since XY must be positive, we can use the positive solution:

XY = (87 + 23m) / 2

Now we can substitute this value for XY in the equation we derived earlier:

13 + (4/5)XY = (10/m)(24 + XY)

13 + (4/5)((87 + 23m) / 2)= (10/m)(24 + (87 + 23m) / 2)

Multiplying both sides by 10m, we get:

130m + 52(87 + 23m) / 10 = (240 + 87m) / 2

Simplifying and solving for m, we get:

1300m + 52(87 + 23m) = 240 + 87m

1300m + 4524 + 1196m = 240 + 87m

2403m = -4284

m = -4284 / 2403

m ≈ -1.78

Therefore, the value of m is approximately -1.78.

User Kolbasov
by
7.8k points

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