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4th grade · Math · Unit 10 of 15

Angles & Area

Acute, right, obtuse and area

What your child practices

Sorting angles into acute, right, obtuse and straight, finding area by multiplying length by width, and working backward to find a side.

Arizona Academic Standards learning standard: 4.MD.C.5; 4.G.A.1; 4.MD.A.3 · lines and angles, acute, right and obtuse angles, and the area formula for rectangles

How we explain it

Children can open this short lesson before they practice.

  1. Area is the space inside. Length × width for a rectangle.
  2. A right angle is a square corner (90°). Acute is smaller. Obtuse is bigger.
  3. Area is measured in square units, like cm².

Example: A rectangle is 4 cm long and 3 cm wide. What is its area? Multiply length by width. 4 × 3 = 12. Answer: 12 square cm

Angles & Area in Arizona

In the Arizona Academic Standards, this is unit 10 of 15 in 4th grade Math, after Fractions 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: Arizona 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 rectangle is 12 cm long and 6 cm wide. What is its area in square centimeters?

    answer box

  2. Question 2

    What kind of angle is this?

    • acute
    • obtuse
    • straight
    • right

  3. Question 3

    A rectangle has an area of 32 square centimeters. It is 8 cm long. How wide is it, in centimeters?

    8 × = 32

    answer box

  4. Question 4

    What kind of angle is the corner of a book?

    • acute angle
    • right angle
    • obtuse angle

  5. Question 5

    What kind of angle is this?

    • right
    • obtuse
    • straight
    • acute

  6. Question 6

    What kind of angle is this?

    • right
    • obtuse
    • straight
    • acute

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