Math Problem Statement

Begin by analyzing the problem: If 100 regular triangles with side lengths of 1 unit are lined up in a row, sharing one side with the adjacent triangle, what will the perimeter of the shape be? Consider the following questions: What will the perimeter of the shape be? What shape do the 100 triangles create? Can you create a rule for finding the perimeter of a shape created by any number of triangles?can you show me how to solve with pictures

If I line up (sharing one side) 100 regular triangles in a row, what will the perimeter be? Can you create a rule for finding the perimeter of a shape created by any number of triangles?

Solution

I see the problem involves determining the perimeter of a shape formed by lining up 100 equilateral triangles, where each triangle shares one side with the next. Let's walk through the solution step by step.

Analysis:

Each regular triangle has three equal sides. When you line up nn triangles in a row, the side they share with adjacent triangles no longer contributes to the perimeter. The key idea is to count how many sides are still exposed.

  1. For 1 triangle: The perimeter is 33 sides.

  2. For 2 triangles: The shared side between the two triangles removes 1 side from the perimeter, leaving: Perimeter=3 (first triangle)+3 (second triangle)2 (shared sides)=4\text{Perimeter} = 3 \text{ (first triangle)} + 3 \text{ (second triangle)} - 2 \text{ (shared sides)} = 4

  3. For 3 triangles: Two sides are shared between adjacent triangles, so: Perimeter=3×32×2=5\text{Perimeter} = 3 \times 3 - 2 \times 2 = 5

General Rule:

If you have nn triangles lined up, the perimeter can be calculated as: Perimeter=2n+1\text{Perimeter} = 2n + 1 This rule works because there are always 2 sides for each triangle plus the unshared sides at the ends.

Solving for 100 triangles:

Using the formula: Perimeter=2×100+1=201\text{Perimeter} = 2 \times 100 + 1 = 201 So the perimeter for 100 triangles is 201 units.

Would you like a visual representation or need further clarification? Let me know if you want to explore any of the following:

  1. How is the perimeter of other polygonal shapes calculated when combined in sequences?
  2. What happens when the triangles are not equilateral or vary in size?
  3. Can the rule be adjusted for different arrangements, like stacking triangles in rows?
  4. What mathematical reasoning underlies the generalization to nn triangles?
  5. What if you try to enclose the shape with other polygons?

Tip:

In any geometric arrangement, identify the shared sides or areas, as this reduces the overall perimeter or surface area.

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Math Problem Analysis

Mathematical Concepts

Geometry
Perimeter Calculation
Sequences

Formulas

Perimeter = 2n + 1

Theorems

Generalization of perimeter formula for linear arrangements of regular polygons

Suitable Grade Level

Grades 6-8