2-min Warm-up — Skip count out loud: count by 2s to 20, then by 5s to 50. Then answer: how many sides does a rectangle have?
Perimeter is the distance all the way AROUND a shape. Imagine an ant walking around the edge — how far does it walk?
Walk around: 3 + 2 + 3 + 2 = 10 units
Your turn: 2 + 2 + 2 + 2 = units
Count the units around each shape. Put a dot where the ant starts so you don't count twice!
Perimeter only today — count the units around the outside edge.
Area: 8 squares
Perimeter: units
Area: 9 squares
Perimeter: units
Area: 5 squares
Perimeter: units
Area: 6 squares
Perimeter: units
Number Talk — Explain WITHOUT counting every single unit.
A rectangle is 4 units long and 2 units wide. Sam counts every unit around: 1, 2, 3... Nia says "4 + 2 + 4 + 2, done!" Whose way is faster? Why does it work?
My thinking:
Two rectangles: one is 5 long and 1 wide, one is 3 long and 3 wide. Which has the bigger perimeter — or are they the same?
My thinking:
Challenge — Show two different ways to find the perimeter of a 3 × 2 rectangle.
Try: (1) counting units around, (2) adding the four sides.
Strategy 1
Perimeter: units
Strategy 2
Perimeter: units