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8th grade · Math · Unit 11 of 17

Congruent Shapes

Slides, flips and turns that keep a shape the same

What your child practices

Recognizing congruent shapes, matching corresponding sides and angles, and finding the coordinates of a point after a slide, flip or turn.

Maine Learning Results learning standard: 8.G.A.2 · congruence through rotations, reflections and translations

How we explain it

Children can open this short lesson before they practice.

  1. Congruent shapes have the same size and shape.
  2. Slides, flips and turns keep a shape congruent.
  3. Matching sides and angles are equal.

Example: A triangle is slid across the page. Is the new triangle congruent? A slide does not change size or shape. So the triangles match. Answer: Yes

Congruent Shapes in Maine

In the Maine Learning Results, this is unit 11 of 17 in 8th grade Math, after Equations with Brackets and before Exponent Rules.

Gradelings describes a child's practice on this unit as Beginning, Approaching, Meeting or Exceeding (Four practice steps). That reflects practice, not a report-card mark: the teacher decides the mark.

Source: Maine Department of Education

Sample questions

A taste of this unit. In the app, questions change every time and get easier or harder to match your child.

  1. Question 1

    A turn about a point is called a…

    • reflection
    • translation
    • dilation
    • rotation

  2. Question 2

    Point A(7, 6) is reflected in the y-axis. What are the coordinates of A′?

    • (-7, 6)
    • (6, 7)
    • (-7, -6)
    • (7, -6)

  3. Question 3

    Which of these keeps a shape congruent?

    • sliding it
    • enlarging it to double its size
    • stretching it taller
    • shrinking it to half its size

  4. Question 4

    In congruent polygons, matching angles and sides are called…

    • adjacent
    • opposite
    • corresponding
    • parallel

  5. Question 5

    Two triangles have sides 3 cm, 4 cm, 5 cm and 3 cm, 4 cm, 6 cm. Are they congruent?

    • only if their angles are 90°
    • yes, two sides match
    • yes, they are both triangles
    • no, one pair of sides is different

  6. Question 6

    Polygon ABCD is congruent to polygon PQRS, with A matching P, B matching Q and so on. If AB = 5 cm, which side must also be 5 cm?

    • PQ
    • QR
    • SP
    • RS

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