Similar Figures and Area Quick Check

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Question
Use the image to answer the question.

A composite figure made up of two rectangles has all of its sides labeled.

If this composite figure were dilated using a scale factor of 3, what would be the area of the dilated figure?

(1 point)
Responses which answer is correct and why

180 square units
180 square units

405 square units
405 square units

45 square units
45 square units

270 square units
270 square units
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1 answer

To determine the area of a dilated figure, we can use the following formula:

  1. When a figure is dilated by a scale factor \( k \), the area of the new figure is given by the formula: \[ \text{Area}{\text{dilated}} = k^2 \times \text{Area}{\text{original}} \]

  2. In this case, the scale factor \( k = 3 \). Thus, \( k^2 = 3^2 = 9 \).

  3. Therefore, the area of the dilated figure will be 9 times the area of the original figure.

To find the correct answer, we need the area of the original figure (which is not provided in your question). However, if we denote the area of the original figure as \( A \), the area of the dilated figure would be:

\[ \text{Area}_{\text{dilated}} = 9A \]

Based on the options provided, you would match \( 9A \) with the possible answers:

  • If \( A = 20 \), then \( \text{Area}_{\text{dilated}} = 180 \) (correct)
  • If \( A = 45 \), then \( \text{Area}_{\text{dilated}} = 405 \) (incorrect)
  • If \( A = 5 \), then \( \text{Area}_{\text{dilated}} = 45 \) (incorrect)
  • If \( A = 30 \), then \( \text{Area}_{\text{dilated}} = 270 \) (incorrect)

Considering the option of 180 square units is correct if the original area was 20 square units. Without knowing the original area, the answer could be \( 180 \text{ square units} \) if this corresponds to a reasonable assumption based on the scale factor of 3.

Thus, if you can confirm that the area of the original figure is indeed 20 square units, then the answer would be:

180 square units.