Math Problem Statement

Segitiga sama kaki memiliki satu sisi dengan panjang lima kali panjang sisi lainnya. Jika keliling segitiga sama kaki paling tidak 60 cm, berapa panjang minimal setiap sisi segitiga?

Solution

Let’s analyze the problem.

The problem describes an isosceles triangle with:

  • Two equal sides.
  • One side that is five times the length of the shorter side.
  • A perimeter of at least 60 cm.

Let the length of the shorter side be xx. Then:

  • Two equal sides each have length xx,
  • The third side is 5x5x,
  • The perimeter is 2x+5x=7x2x + 5x = 7x.

Step 1: Solve for xx

The perimeter condition says: 7x607x \geq 60 x6078.57cm.x \geq \frac{60}{7} \approx 8.57 \, \text{cm}.

Thus, the minimum integer value of xx is 99 cm.

Step 2: Verify the side lengths

  • The shorter sides: x=9cmx = 9 \, \text{cm},
  • The longer side: 5x=45cm5x = 45 \, \text{cm}.

The sides 9,9,459, 9, 45 satisfy the triangle inequality rule:

  1. 9+9>459 + 9 > 45 is not true (the sides cannot form a triangle).

To satisfy the inequality, we need to increase xx.

Step 3: Adjust xx for triangle inequality

For the inequality 2x>5x2x > 5x, we simplify: x>452=22.5cm.x > \frac{45}{2} = 22.5 \, \text{cm}.

So, the minimum value of xx is 23cm23 \, \text{cm}.

Final Answer:

  • The shorter sides are 23cm23 \, \text{cm},
  • The longer side is 5(23)=115cm5(23) = 115 \, \text{cm}.

The minimum side lengths are: 23,23,115cm.23, 23, 115 \, \text{cm}.

Let me know if you’d like further explanation or details! Here are 5 related questions:

  1. How does the triangle inequality rule work?
  2. Can we solve similar problems for different perimeters?
  3. What is the general approach to solving isosceles triangle problems?
  4. How can this problem be represented graphically?
  5. What are other real-world applications of the triangle inequality?

Tip: Always verify all constraints, especially the triangle inequality, when solving triangle-related problems!

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Math Problem Analysis

Mathematical Concepts

Algebra
Geometry
Triangle Inequality
Perimeter of Triangles

Formulas

Perimeter of a triangle: P = a + b + c
Triangle inequality: a + b > c

Theorems

Triangle Inequality Theorem

Suitable Grade Level

Grades 7-10