Math Problem Statement

Solving Applications with Proportional Reasoning Christianne has a full size tree and a young tree in her backyard. She notices the shadows of the tree and realizes the ratios of the shadow height to tree height are proportional. She made the sketch below to organize her information and realized she could make a geometric model with similar triangles.

Christianne measure the shadow heights and finds that the shadow of the young tree is feet and the shadow of the full size tree is feet. Use this information to find the ratios below. Find the ratio:

Unsimplified:

Simplified:

Find the ratio:

Unsimplified:

Simplified:

Suppose Christianne measures the young tree and determines it is feet. How tall is the full size tree?

feet

Round your answer to two decimal places Suppose Christianne realizes the full size tree is approximately the same height as her house which is feet. How tall is the young tree?

feet

Round your answer to two decimal places

Solution

To solve this problem, we need to rely on proportional reasoning using the similar triangles created by the trees and their shadows.

Step-by-Step Breakdown:

  1. Determine the Ratios: Since the triangles formed by the trees and their shadows are proportional, the ratio of the shadow length to the tree height for both the young tree and the full-size tree must be the same.

Let:

  • hyh_y be the height of the young tree
  • hfh_f be the height of the full-size tree
  • sys_y be the shadow length of the young tree
  • sfs_f be the shadow length of the full-size tree

We can set up the proportional relationship as:

syhy=sfhf\frac{s_y}{h_y} = \frac{s_f}{h_f}

Given that both ratios are equal, we can use this to solve for the unknown heights, provided we have some measurements.


Example Solutions:

1. Unsimplified Ratios:

  • The unsimplified ratios are the raw fractions of shadow length over tree height, based on measurements taken by Christianne.

Ratio of Young Tree: syhy\text{Ratio of Young Tree: } \frac{s_y}{h_y} Ratio of Full-Size Tree: sfhf\text{Ratio of Full-Size Tree: } \frac{s_f}{h_f}

2. Simplified Ratios:

  • The simplified ratios are the fractions reduced to their simplest form by dividing the numerator and denominator by their greatest common divisor (GCD).

3. Find the Height of the Full-Size Tree:

Suppose Christianne measured the young tree to be hyh_y feet and we know the shadow lengths sys_y and sfs_f (shadow of the full-size tree). We can solve for hfh_f using the proportion:

syhy=sfhf\frac{s_y}{h_y} = \frac{s_f}{h_f}

Solving for hfh_f (the height of the full-size tree):

hf=sfhysyh_f = \frac{s_f \cdot h_y}{s_y}

Plug in the values for sys_y, hyh_y, and sfs_f to find hfh_f, and then round the answer to two decimal places.


4. Find the Height of the Young Tree:

If Christianne determines that the full-size tree (or house) is hfh_f feet tall, and we know the shadow lengths, we can use the same proportion to solve for the height of the young tree:

hy=syhfsfh_y = \frac{s_y \cdot h_f}{s_f}

Substitute the known values and round the result to two decimal places.


Let me know if you have the specific measurements, and I can help calculate the exact ratios and heights for you.


5 Related Questions:

  1. What is the significance of proportional reasoning in solving geometric problems?
  2. How does the concept of similar triangles apply to real-life situations like measuring tree heights?
  3. Can you explain how to simplify a ratio?
  4. How do changes in the shadow length affect the height calculations of the tree?
  5. How can you check if two triangles are similar using proportional reasoning?

Tip: Always remember that in proportional reasoning, corresponding sides of similar triangles must have equal ratios!

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Math Problem Analysis

Mathematical Concepts

Proportional Reasoning
Geometry
Similar Triangles

Formulas

Ratio formula: s_y / h_y = s_f / h_f
Height of the full-size tree: h_f = (s_f * h_y) / s_y
Height of the young tree: h_y = (s_y * h_f) / s_f

Theorems

Proportionality Theorem
Similarity of Triangles

Suitable Grade Level

Grades 6-8