An engineer is planning to construct triangular halls on a new construction site. A scale model of the engineer's triangular halls is shown below. Each unit represents 10 feet.

Hall A has vertices at (-4, 0), (-2, 2), (-2, -2), Hall B has vertices at (4, 0), (2, -2), (2, 2), Hall C has its vertices at (5, -5), (10, 0), (5, 5).

Which of the following statements are true about this scale model? Select three statements that apply.
A.
Hall C is similar to Hall A.

B.
Hall C is similar to Hall B.

C.
Hall C is congruent to Hall A.

D.
Hall B is congruent to Hall A.

E.
The scale factor of dilation applied to Hall B to produce Hall C is 5.

1 answer

To determine the relationships and similarities between the triangles representing the halls, we need to analyze the given vertices and their respective lengths and angles.

  1. Hall A vertices:

    • A: (-4, 0)
    • B: (-2, 2)
    • C: (-2, -2)

    Calculating the side lengths using the distance formula:

    • AB = √[(-2 + 4)² + (2 - 0)²] = √(2² + 2²) = √8 = 2√2
    • AC = √[(-2 + 4)² + (-2 - 0)²] = √(2² + 2²) = √8 = 2√2
    • BC = √[(-2 + 2)² + (2 + 2)²] = √(0² + 4²) = 4
  2. Hall B vertices:

    • A: (4, 0)
    • B: (2, -2)
    • C: (2, 2)

    Following the same calculations for lengths:

    • AB = √[(2 - 4)² + (-2 - 0)²] = √(-2)² + (-2)² = √8 = 2√2
    • AC = √[(2 - 4)² + (2 - 0)²] = √(-2)² + 2² = √8 = 2√2
    • BC = √[(2 - 2)² + (2 + 2)²] = √(0² + 4²) = 4
  3. Hall C vertices:

    • A: (5, -5)
    • B: (10, 0)
    • C: (5, 5)

    Again, compute the side lengths:

    • AB = √[(10 - 5)² + (0 + 5)²] = √(5² + 5²) = √50 = 5√2
    • AC = √[(5 - 5)² + (5 + 5)²] = √(0 + 10²) = 10
    • BC = √[(10 - 5)² + (5 - 0)²] = √(5² + 5²) = √50 = 5√2

Now we can evaluate each option:

A. Hall C is similar to Hall A.

  • Not true. The side lengths are not proportional; Hall C has sides of \( (5√2, 10, 5√2) \) and Hall A has sides \( (2√2, 2√2, 4) \).

B. Hall C is similar to Hall B.

  • True. The ratios of their corresponding sides give a consistent ratio of 5:2 (for example, \( \frac{5√2}{2√2} = 2.5 \) and \( \frac{10}{4} = 2.5 \)).

C. Hall C is congruent to Hall A.

  • Not true. The triangles are not the same size as they do not have equal lengths.

D. Hall B is congruent to Hall A.

  • True. They have the same side lengths: \( 2√2, 2√2, 4 \).

E. The scale factor of dilation applied to Hall B to produce Hall C is 5.

  • True. Appearance suggests that Hall C is a scaled up version of Hall B by a factor of \( 5/2 \), however more directly, looking at the side lengths confirms \( 5:2 \) for sides.

The three true statements are:

  • B. Hall C is similar to Hall B.
  • D. Hall B is congruent to Hall A.
  • E. The scale factor of dilation applied to Hall B to produce Hall C is 5.

Thus, the selected statements are B, D, and E.