Math Problem Statement

Suppose you are standing such that a 30-foot tree is directly between you and the sun. If you are 6 feet tall and the tree casts a 50-foot shadow, how far away from the tree can you stand and still be completely in the shadow of the tree?

Solution

To solve this problem, we can use similar triangles, as the angles between the sun’s rays, the tree, and its shadow are the same as the angles between the sun’s rays, you, and your shadow.

Here's a step-by-step approach:

  1. Set Up the Triangles:

    • The tree and its shadow form a right triangle where:
      • The height of the tree is 3030 feet.
      • The shadow of the tree is 5050 feet.
    • You, being 66 feet tall, would have a proportional shadow length that depends on your distance from the tree.
  2. Calculate the Shadow Proportion: Using the similarity of triangles, we set up the following proportion based on the heights and shadow lengths:

    Height of treeShadow of tree=Your heightYour shadow length\frac{\text{Height of tree}}{\text{Shadow of tree}} = \frac{\text{Your height}}{\text{Your shadow length}}

    Substituting values:

    3050=6Your shadow length\frac{30}{50} = \frac{6}{\text{Your shadow length}}

  3. Solve for Your Shadow Length: Cross-multiply to find your shadow length:

    30×Your shadow length=6×5030 \times \text{Your shadow length} = 6 \times 50

    30×Your shadow length=30030 \times \text{Your shadow length} = 300

    Your shadow length=30030=10 feet\text{Your shadow length} = \frac{300}{30} = 10 \text{ feet}

  4. Determine Your Position Relative to the Tree: Since the tree’s shadow is 5050 feet long, and your shadow length is 1010 feet, you need to be within the length of the tree's shadow to be fully covered by it. Thus, you can stand anywhere up to 5010=4050 - 10 = 40 feet away from the tree and remain completely in its shadow.

Final Answer:

You can stand up to 40 feet away from the tree and still be completely in the shadow of the tree.

Would you like further details or have any questions?


Here are some questions to deepen understanding:

  1. How would the solution change if the height of the tree was doubled?
  2. What happens to the distance you can stand away from the tree if your height increases?
  3. How would the calculation change if the sun were at a lower angle?
  4. If the shadow of the tree were shorter, how would it affect your maximum distance?
  5. How would this apply if you had multiple trees in a row?

Tip: Always draw a diagram for problems involving similar triangles and proportional relationships to visualize the relationships between elements.

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Math Problem Analysis

Mathematical Concepts

Similar Triangles
Proportions

Formulas

Proportion formula: (height1 / shadow1) = (height2 / shadow2)

Theorems

Similarity Theorem

Suitable Grade Level

Grades 7-10