Math Problem Statement

In the figure below, AC || DE, BD measures 8 m, AD measures 12 m, and BE measures 10 m. Find the length of BC.

Solution

We are given the following information from the image:

  • ACDEAC \parallel DE
  • BD=8mBD = 8 \, \text{m}
  • AD=12mAD = 12 \, \text{m}
  • BE=10mBE = 10 \, \text{m}

We need to find the length of BCBC.

Since ACDEAC \parallel DE, the triangles ABD\triangle ABD and EBC\triangle EBC are similar by the Basic Proportionality Theorem (also known as Thales' theorem). This means corresponding sides are proportional.

Using the similarity property: ADBD=BEBC\frac{AD}{BD} = \frac{BE}{BC} Substituting the known values: 128=10BC\frac{12}{8} = \frac{10}{BC} Now we solve for BCBC: 128=32,32=10BC\frac{12}{8} = \frac{3}{2}, \quad \frac{3}{2} = \frac{10}{BC} Cross-multiplying: 3BC=2103BC=203 \cdot BC = 2 \cdot 10 \quad \Rightarrow \quad 3 \cdot BC = 20 BC=2036.67mBC = \frac{20}{3} \approx 6.67 \, \text{m}

Thus, the length of BCBC is approximately 6.67 meters.

Do you need more details or have any questions?


Here are 5 related questions:

  1. What is the Basic Proportionality Theorem?
  2. How do we identify similar triangles in geometric figures?
  3. Why does ACDEAC \parallel DE imply similarity of triangles?
  4. What would happen if the triangles weren't similar? Could we still find BCBC?
  5. How does Thales' theorem apply in coordinate geometry?

Tip: When triangles are similar, all corresponding sides and angles maintain a constant ratio, making it easier to calculate unknown dimensions using proportions.

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Math Problem Analysis

Mathematical Concepts

Geometry
Similar Triangles
Proportions

Formulas

(AD / BD) = (BE / BC)

Theorems

Basic Proportionality Theorem (Thales' Theorem)

Suitable Grade Level

Grades 9-10