Triangle Similarity Problem

MathematicsGeometryMedium

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Given a triangle with a base of $20$, and a line segment $x$ parallel to the base that divides the sides. The left side is divided into two segments of length $4$ each. The right side is divided into two segments, the top $y$ and the bottom $6$. Calculate $x + y$.

This question includes visual content: A hand-drawn triangle with a horizontal line segment inside, parallel to the base. The base of the large triangle is labeled 20. The left side of the large triangle is divided into two segments of length 4, with an arrow indicating that the top segment and bottom segment are both 4. The right side is divided into two segments, the top labeled y and the bottom labeled 6. The internal horizontal segment is labeled x. The question asks for x + y.

Animated Video Solution

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Step by Step Written Solution

1
Step 1

Hi salma, let's solve this geometry problem together. We are given a large triangle with a horizontal line segment inside it, and we need to find the sum of x and y.

Finding $x + y$

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Step 2

Looking at the diagram, we see a horizontal line segment of length x inside a larger triangle with a base of twenty. Because this line is horizontal, it is parallel to the base, creating a smaller similar triangle at the top.

20x44y6
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Step 3

Let's first find the value of x. The side lengths of the small top triangle are proportional to the side lengths of the large triangle. The left side of the small triangle is four, and the left side of the entire large triangle is four plus four which is eight.

$$\frac{\text{Small Side}}{\text{Large Side}} = \frac{\text{Small Base}}{\text{Large Base}}$$
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Step 4

Substituting our known values, we get four over eight equals x over twenty.

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Step 5

The fraction four over eight simplifies to one half. So, one half equals x over twenty.

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Step 6

Multiplying both sides by twenty, we find that x equals ten.

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Step 7

Now let's find the value of y using the same proportionality. The ratio of the segments on the right side must equal the ratio of the segments on the left side, or we can use the similar triangle ratios again.

Calculating y

$$\frac{\text{Left Top}}{\text{Left Bottom}} = \frac{\text{Right Top}}{\text{Right Bottom}}$$

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About This Question

Subject
Mathematics
Topic
Geometry
Difficulty
Medium
Question Type
Open Ended

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