Math Problem Statement

For a project in her Geometry class, Caroline uses a mirror on the ground to measure the height of her school’s flagpole. She walks a distance of 6.35 meters from the flagpole, then places a mirror flat on the ground, marked with an X at the center. She then walks 4.1 more meters past the mirror, so that when she turns around and looks down at the mirror, she can see the top of the flagpole clearly marked in the X. Her partner measures the distance from her eyes to the ground to be 1.35 meters. How tall is the flagpole? Round your answer to the nearest hundredth of a meter.

Answer

Solution

To determine the height of the flagpole, we will use the concept of similar triangles. Here's the reasoning step-by-step:


Step 1: Understanding the Geometry

  • The mirror creates two similar right triangles:
    1. Triangle 1: From the top of the flagpole to the mirror on the ground.
    2. Triangle 2: From Caroline's eyes to the mirror on the ground.

Since the reflection of the flagpole in the mirror aligns perfectly with Caroline's line of sight, the triangles are similar.


Step 2: Setting Up the Known Values

Let:

  • hh be the height of the flagpole (what we want to find).
  • d1d_1 be the distance from the flagpole to the mirror: d1=6.35md_1 = 6.35 \, \text{m}.
  • d2d_2 be the distance from the mirror to Caroline: d2=4.1md_2 = 4.1 \, \text{m}.
  • h2h_2 be the height of Caroline's eyes above the ground: h2=1.35mh_2 = 1.35 \, \text{m}.

Because the triangles are similar, the following proportion holds:

Height of FlagpoleDistance to Mirror from Flagpole=Height of Caroline’s EyesDistance to Mirror from Caroline.\frac{\text{Height of Flagpole}}{\text{Distance to Mirror from Flagpole}} = \frac{\text{Height of Caroline's Eyes}}{\text{Distance to Mirror from Caroline}}.

Mathematically, this is:

h6.35=1.354.1.\frac{h}{6.35} = \frac{1.35}{4.1}.


Step 3: Solving for hh

  1. First, calculate the ratio 1.354.1\frac{1.35}{4.1}:

1.354.10.3293.\frac{1.35}{4.1} \approx 0.3293.

  1. Use the proportion to find hh:

h=6.35×0.3293.h = 6.35 \times 0.3293.

Performing the multiplication:

h2.09meters.h \approx 2.09 \, \text{meters}.


Final Answer:

The height of the flagpole is approximately 2.09 meters.


Do you want a visual explanation or further clarification? Let me know!

Here are 5 related questions you might explore:

  1. What are similar triangles, and how do they relate to reflections?
  2. How can mirrors be used in real-life geometry problems?
  3. If Caroline's eye height changed, how would it affect the height of the flagpole?
  4. Can this method work if the ground is not perfectly flat?
  5. What are some other indirect measurement techniques in geometry?

Tip: Always check for triangle similarity when reflections are involved in geometry!

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Math Problem Analysis

Mathematical Concepts

Geometry
Similar Triangles
Proportions

Formulas

h / d₁ = h₂ / d₂

Theorems

Triangle Similarity Theorem

Suitable Grade Level

Grades 8-10