Using the State Curriculum: Mathematics, Grade 3

• How do you find the perimeter of a figure? [Count the units around the outside of the figure.]
• What is the perimeter of figure C? [22 units]
• Which figure has the greatest perimeter? [C]
• Which figure has the least? [D]
• Which two figures have the same perimeter? [A & B] Are their areas the same? [No, Figure A's area is 25 sq. units but Figure B's area is 24 sq. units.]

• Julia is building a square picture frame for her school photo. The frame has a perimeter of 16 units. Draw the picture frame on the grid below
• What is the length of each side? [4 units]

  

• If she enlarges her picture frame by 1 unit on each side, what will the new perimeter be? [20 units] Explain why your answer is correct. [By adding one unit to each side, the length of each side is now 5 since 4 + 1 = 5. The perimeter becomes 20 units since 5 + 5 + 5 + 5 = 20.]
• What if she enlarges the picture frame by 2 units? By 3 units?
  2 Units: [Increasing each side by 2 units makes the perimeter 24 units.
  4 + 2 = 6     6 + 6 + 6 + 6 = 24]
  3 Units: [Increasing each side by 3 units makes the perimeter 28 units.
  4 + 3 = 7     7 + 7 + 7 + 7 = 28]

• David is making business magnets for his lawn mowing business. The business cards have a perimeter of 24 units. On grid paper, draw at least 4 different ways that David's business cards could look.

Answers:

• David wants his business magnets to really show up and have the largest area. Which rectangle should he choose? [The 6 unit × 6 unit square]
• David decided he wanted the perimeter of his business magnets to be 40 units and have the largest area. What are the dimensions of the new magnet? [A 10 unit × 10 unit square]