Lesson Worksheet: Triangle Similarity Criteria and Their Applications Mathematics

In this worksheet, we will practice using the properties of similar triangles to solve problems.

Q1:

The figure shows a triangle 𝐴𝐷𝐸 where the line segment 𝐵𝐶 is parallel to 𝐷𝐸

Which angle is equivalent to 𝐴𝐵𝐶? Give reasons.

  • A𝐴𝐶𝐵, because the angles are corresponding.
  • B𝐴𝐷𝐸, because the angles are corresponding.
  • C𝐴𝐸𝐷, because the angles are corresponding.
  • D𝐴𝐷𝐸, because the angles are alternate.
  • E𝐴𝐶𝐵, because the angles are alternate.

Which angle is equivalent to 𝐴𝐶𝐵? Give reasons.

  • A𝐴𝐵𝐶, because the angles are corresponding.
  • B𝐴𝐸𝐷, because the angles are corresponding.
  • C𝐴𝐷𝐸, because the angles are corresponding.
  • D𝐴𝐷𝐸, because the angles are alternate.
  • E𝐴𝐸𝐷, because the angles are alternate.

Hence, are triangles 𝐴𝐵𝐶 and 𝐴𝐷𝐸 similar? If yes, state why?

  • AYes, they are similar by the SAS criterion.
  • BNo
  • CYes, they are similar by the AA criterion.
  • DYes, they are similar by the SSS criterion.

Q2:

The figure shows two triangles 𝐴𝐵𝐶 and 𝐷𝐸𝐶 where the line segment 𝐴𝐵 is parallel to 𝐷𝐸.

Which angle is equivalent to 𝐴𝐵𝐶? Give reasons.

  • A𝐶𝐸𝐷, because the angles are alternate
  • B𝐶𝐷𝐸, because the angles are corresponding
  • C𝐶𝐸𝐷, because the angles are corresponding
  • D𝐷𝐶𝐸, because the angles are vertically opposite
  • E𝐶𝐷𝐸, because the angles are alternate

Which angle is equivalent to 𝐵𝐴𝐶? Give reasons.

  • A𝐶𝐸𝐷, because the angles are corresponding
  • B𝐶𝐷𝐸, because the angles are alternate
  • C𝐶𝐸𝐷, because the angles are alternate
  • D𝐶𝐷𝐸, because the angles are corresponding
  • E𝐷𝐶𝐸, because the angles are vertically opposite

Hence, are triangles 𝐴𝐵𝐶 and 𝐷𝐸𝐶 similar? If yes, state why.

  • ANo
  • BYes, they are similar by the SSS criterion.
  • CYes, they are similar by the AA criterion.
  • DYes, they are similar by the SAS criterion.

Q3:

In the figure, 𝐶𝐵=5.7 and 𝐵𝐸=9.12. Since triangles 𝐶𝐵𝐴 and 𝐸𝐵𝐷 are similar, what is the scale factor?

Q4:

In trapezoid 𝐴𝐵𝐶𝐷, sides 𝐴𝐷 and 𝐵𝐶 are parallel, and its diagonals intersect at 𝑀. Given that 𝐴𝐷=66, 𝐵𝐶=33, and 𝐴𝐶=75, what is the length of 𝑀𝐴?

Q5:

The figure shows triangle 𝐴𝐵𝐶.

Work out the value of 𝑥.

Work out the value of 𝑦.

Work out the perimeter of 𝐴𝐵𝐶.

Q6:

The given figure shows a right triangle 𝐴𝐵𝐶, where 𝐶𝐷 is perpendicular to 𝐴𝐵.

Using similarity, express 𝑎 in terms of 𝑐 and 𝑑.

  • A𝑎=𝑐𝑑
  • B𝑎=(𝑐𝑑)
  • C𝑎=𝑐𝑑
  • D𝑎=(𝑐𝑑)
  • E𝑎=𝑐𝑑

Using similarity, express 𝑏 in terms of 𝑐 and 𝑒.

  • A𝑏=𝑐𝑒
  • B𝑏=𝑐𝑒
  • C𝑏=𝑐𝑒
  • D𝑏=(𝑐𝑒)
  • E𝑏=(𝑐𝑒)

Express the sum of 𝑎 and 𝑏 in terms of 𝑐.

  • A𝑎+𝑏=𝑐2
  • B𝑎+𝑏=2𝑐
  • C𝑎+𝑏=𝑐
  • D𝑎+𝑏=𝑐
  • E𝑎+𝑏=2𝑐

Q7:

If 𝐴𝐵𝐷𝐴𝐶𝐵, find 𝑚𝐷𝐵𝐶 and the length of 𝐶𝐷 to the nearest tenth.

  • A71, 23.4 cm
  • B32, 19 cm
  • C39, 23.4 cm
  • D39, 15 cm

Q8:

In the given figure, 𝐷𝐸 and 𝐵𝐶 are parallel. Use similarity to work out the value of 𝑥.

  • A𝑥=68
  • B𝑥=3
  • C𝑥=1
  • D𝑥=6
  • E𝑥=5

Q9:

Triangles 𝐴𝐵𝐶 and 𝐴𝐷𝐸 are similar. Find 𝑥 to the nearest integer.

Q10:

A 1.97-meter-tall man stands 3.49 m away from a streetlight and casts a shadow that is 2.73 m long. How high is the lamp? Round your answer to the nearest tenth.

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