Which sets of potential side lengths make a triangle?

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Understand the Problem

The question is asking to determine which sets of potential side lengths can form a triangle based on the triangle inequality theorem, which states that the sum of the lengths of any two sides must be greater than the length of the remaining side.

Answer

- Makes a Triangle: 2.4 mm, 5.7 mm, 7.9 mm; 3.1 cm, 3.1 cm, 6.1 cm; 18.23 ft, 18.23 ft, 18.23 ft - Does Not Make a Triangle: 3 in, 5 in, 8 in; 5 cm, 7 cm, 13 cm
Answer for screen readers
  • Makes a Triangle: 2.4 mm, 5.7 mm, 7.9 mm; 3.1 cm, 3.1 cm, 6.1 cm; 18.23 ft, 18.23 ft, 18.23 ft
  • Does Not Make a Triangle: 3 in, 5 in, 8 in; 5 cm, 7 cm, 13 cm

Steps to Solve

  1. Identify the side lengths

    We have the following sets of side lengths to analyze:

    • Set 1: $3 , \text{in}, 5 , \text{in}, 8 , \text{in}$
    • Set 2: $5 , \text{cm}, 7 , \text{cm}, 13 , \text{cm}$
    • Set 3: $2.4 , \text{mm}, 5.7 , \text{mm}, 7.9 , \text{mm}$
    • Set 4: $3.1 , \text{cm}, 3.1 , \text{cm}, 6.1 , \text{cm}$
    • Set 5: $18.23 , \text{ft}, 18.23 , \text{ft}, 18.23 , \text{ft}$
  2. Apply the triangle inequality theorem

    According to the triangle inequality theorem, for any three side lengths (a), (b), and (c):

    $$ a + b > c $$ $$ a + c > b $$ $$ b + c > a $$

    We will examine each set of lengths to see if they satisfy these conditions.

  3. Evaluate each set

    • Set 1: $3 , \text{in}, 5 , \text{in}, 8 , \text{in}$

      • Check:
        • $3 + 5 = 8 \not> 8$ (fails).
    • Set 2: $5 , \text{cm}, 7 , \text{cm}, 13 , \text{cm}$

      • Check:
        • $5 + 7 = 12 < 13$ (fails).
    • Set 3: $2.4 , \text{mm}, 5.7 , \text{mm}, 7.9 , \text{mm}$

      • Check:
        • $2.4 + 5.7 = 8.1 > 7.9$ (passes).
        • $2.4 + 7.9 = 10.3 > 5.7$ (passes).
        • $5.7 + 7.9 = 13.6 > 2.4$ (passes).
      • Therefore, this set makes a triangle.
    • Set 4: $3.1 , \text{cm}, 3.1 , \text{cm}, 6.1 , \text{cm}$

      • Check:
        • $3.1 + 3.1 = 6.2 > 6.1$ (passes).
        • $3.1 + 6.1 = 9.2 > 3.1$ (passes).
        • $3.1 + 6.1 = 9.2 > 3.1$ (passes).
      • Therefore, this set makes a triangle.
    • Set 5: $18.23 , \text{ft}, 18.23 , \text{ft}, 18.23 , \text{ft}$

      • All sides are equal, so by property of equilateral triangles:
        • Each condition is satisfied, thus it makes a triangle.
  4. Conclusion

    From the analysis:

    • Set 3, Set 4, and Set 5 make a triangle.
    • Set 1 and Set 2 do not make a triangle.
  • Makes a Triangle: 2.4 mm, 5.7 mm, 7.9 mm; 3.1 cm, 3.1 cm, 6.1 cm; 18.23 ft, 18.23 ft, 18.23 ft
  • Does Not Make a Triangle: 3 in, 5 in, 8 in; 5 cm, 7 cm, 13 cm

More Information

The triangle inequality theorem is crucial in determining whether three lengths can form a triangle. Sets of lengths where the sum of any two sides is greater than the third side will always be able to form a triangle.

Tips

  • Misapplying the inequalities: Remember that the sum must be strictly greater than the third side; equality does not count.
  • Failing to evaluate all three inequalities: Always check all combinations for completeness.

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