Dilations, Similarity, Scale Factor

Which of the following is the algebraic representation for a dilation?

• (x, y) → (x, 3y)

• (x, y) → (3x, 3y)

• (x, y) → (x, y - 3)

• (x, y) → (.5x, .4y)

Are the two polygons similar? If not, explain why. (They are not drawn to scale, but you can assume all angles are 90°.)

• Yes

• No; Not enough information to tell

• No; 5 ⁄ 25 ≠ 6 ⁄ 10

• No; 5 ⁄ 25 ≠ 8 ⁄ 41

Find the scale factor of the dilation. Then tell whether the dilation is a reduction or an enlargement.

• 2 / 5; reduction

• 5 / 2; enlargement

• 2 / 3; reduction

• 3 / 2; enlargement

Describe the similarity transformation that maps to (dilations have a center at the origin).

• a dilation with a scale factor of 2 followed by a translation 4 units right and 3 units down.

• a dilation with a scale factor of 1 / 2 followed by a translation 4 units left and 3 units up.

• Translation 4 units right and 3 units down followed by a dilation with a scale factor 2.

• Translation 4 units left and 3 units up followed by a dilation with a scale factor 1 / 2.

The two polygons are similar.

Find the value of x

Find the scale factor

Find the ratio of the perimeter.

Value of x: ____, Scale factor: ____, Ratio of perimeter: ____

How do you write the algebraic notation when the scale factor is 1/2?

• (x, y) −> (2x, 2y)

• (x, y) −> (1/2x, 1/2y)

• (x, y) −> (-2x, -2y)

• (x, y) −> (2x, 1/2y)

If two polygons are SIMILAR, then the corresponding sides must be _____.

• Congruent

• Proportional

• Parallel

• similar

Which of the statements is true about the graphed triangles?

• They are similar, because one can be obtained by dilating the other about the origin with a scale factor of 2.

• They are similar, because one can be obtained by dilating the other about the origin with a scale factor of 1/2.

• They are not similar, because one can be obtained by dilating the other about the origin with a scale factor of 2.

• They are not similar, because one can be obtained by dilating the other about the origin with a scale factor of 1/2.

The pair of figures is similar. Find the missing side.

• x = 20

• x = 12

• x = 5

• x = 4

Pentagon ABCDE is similar to Pentagon RYMNT. Which of the following is correct.

• ∠C ≅ ∠M

• ∠T ≅ ∠E

• ∠Y ≅ ∠B

• ∠A ≅ ∠M

• ∠C ≅ ∠R