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3rd grade · Math · Unit 10 of 16

Area & Perimeter

Around and inside shapes

What your child practices

Finding the perimeter (distance around) of rectangles and triangles, finding a missing side, and measuring area in square centimeters and square meters.

New York State Learning Standards learning standard: NY-3.MD.5; NY-3.MD.6; NY-3.MD.7; NY-3.MD.8 · measuring area with unit squares, relating area to multiplication, and solving perimeter problems

How we explain it

Children can open this short lesson before they practice.

  1. Perimeter is the distance around a shape. Add all sides.
  2. Area is the space inside. Count the square units.
  3. Perimeter uses cm. Area uses square cm.

Example: A rectangle is 5 cm long and 3 cm wide. What is its perimeter? Add all four sides: 5 + 3 + 5 + 3. That is 16 cm. Answer: 16 cm

Area & Perimeter in New York

In the New York State Learning Standards, this is unit 10 of 16 in 3rd grade Math, after Round & Count and before Sorting Polygons.

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: New York State Education Department (NYSED)

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 7 cm long and 5 cm wide. What is its area, in square centimeters?

    • 29
    • 36
    • 35

  2. Question 2

    A triangle has sides of 5 cm, 3 cm and 4 cm. What is its perimeter in centimeters?

    answer box

  3. Question 3

    Which rectangle has the same area as a 2 by 6 rectangle?

    • 1 by 12
    • 3 by 6
    • 1 by 13

  4. Question 4

    A rectangle is 10 cm long and 7 cm wide. What is its area, in square centimeters?

    • 64
    • 65
    • 70

  5. Question 5

    A rectangle is 7 cm long and 2 cm wide. What is its perimeter in centimeters?

    • 22
    • 14
    • 18

  6. Question 6

    Which unit is best for the area of a postage stamp?

    • centimeters
    • square centimeters
    • square meters

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