Math Problem Statement

In the given figure, ΔABC ~ ΔCDE and BCD is a straight line. If ∠B = 90°, AC = 12 cm and 5CE = 2AC + 1, then the length of AE is?

Solution

To solve this problem, we need to use the properties of similar triangles. The question tells us that triangles ABC\triangle ABC and CDE\triangle CDE are similar (ABCCDE\triangle ABC \sim \triangle CDE), and we know the following information:

  1. B=90\angle B = 90^\circ.
  2. AC=12AC = 12 cm.
  3. 5CE=2AC+15CE = 2AC + 1.
  4. We are asked to find the length of AEAE.

Step-by-Step Solution:

1. Using Similarity of Triangles

Since ABCCDE\triangle ABC \sim \triangle CDE, the sides of these triangles are proportional. Therefore, we can set up a ratio between the corresponding sides:

ABBC=CDDE=ACCE\frac{AB}{BC} = \frac{CD}{DE} = \frac{AC}{CE}

2. Substitute AC=12AC = 12 and Use the Equation for CECE

We have AC=12AC = 12 cm. Using the equation 5CE=2AC+15CE = 2AC + 1:

5CE=2×12+15CE = 2 \times 12 + 1 5CE=24+15CE = 24 + 1 5CE=255CE = 25 CE=255=5 cmCE = \frac{25}{5} = 5 \text{ cm}

3. Set Up the Proportional Ratios to Find AEAE

Since ABCCDE\triangle ABC \sim \triangle CDE, and we now know AC=12AC = 12 cm and CE=5CE = 5 cm, we can use these proportions to determine the length of AEAE:

AEAC=ACCE\frac{AE}{AC} = \frac{AC}{CE}

Substitute AC=12AC = 12 and CE=5CE = 5:

AE12=125\frac{AE}{12} = \frac{12}{5}

Cross-multiplying to solve for AEAE:

[ AE = \frac{12 \times 12}{5} = \frac{144}{5} = 12 \sqrt{5} \approx 12 \times 2.24 = 26.88 \

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Math Problem Analysis

Mathematical Concepts

Similarity of Triangles
Proportions

Formulas

Proportionality of sides in similar triangles: (AB / BC) = (CD / DE) = (AC / CE)
Equation setup for similar triangles: (AE / AC) = (AC / CE)

Theorems

Similarity Theorem
Proportionality in Similar Triangles

Suitable Grade Level

Grades 9-10