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4th grade · Math · Unit 13 of 17

Triangles, Quadrilaterals & Angles

Name shapes by their sides and angles, and find missing angles

What your child practices

Triangles are named by their sides (equilateral, isosceles, scalene) and by their angles (acute, right, obtuse). Quadrilaterals include squares, rectangles, rhombuses, parallelograms and trapezoids. Complementary angles add to 90° and supplementary angles add to 180°.

Texas Essential Knowledge and Skills (TEKS) teks student expectation: 4.6(C); 4.7(E) · acute, right and obtuse triangles, and finding an unknown angle from two adjacent angles

How we explain it

Children can open this short lesson before they practice.

  1. Triangles by angles: acute, right or obtuse.
  2. A trapezoid has exactly one pair of parallel sides.
  3. A right angle is 90°. Acute is less. Obtuse is more.

Example: A triangle has angles 27°, 90° and 63°. What kind is it? One angle is 90°, a right angle. So it is a right triangle. Answer: A right triangle

Triangles, Quadrilaterals & Angles in Texas

In the Texas Essential Knowledge and Skills (TEKS), this is unit 13 of 17 in 4th grade Math, after Polygons & Perimeter and before Metric Measures.

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: Texas Education Agency (TEA)

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

    Two angles are supplementary. One angle is 158°. What is the other angle?

    answer box°

  2. Question 2

    Two angles are supplementary. One angle is 133°. What is the other angle?

    answer box°

  3. Question 3

    How many sides does every quadrilateral have?

    • 6
    • 5
    • 4
    • 3

  4. Question 4

    Which pair of angles is supplementary?

    • 30° and 150°
    • 30° and 60°
    • 30° and 140°
    • 30° and 160°

  5. Question 5

    How many right angles does a square have?

    • 2
    • 0
    • 4
    • 3

  6. Question 6

    Which has opposite sides that are parallel and equal?

    • triangle
    • pentagon
    • trapezoid
    • parallelogram

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