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Intro to Geometry: Curved or Straight

Sweet Pea is 43 months old.

From: I found this really quick activity at Sunbeams and Sanity, who found it on Montessori for Everyone.


  • Scissors.
  • Pen.
  • Tray (optional).
  • A laminator or press and seal lamination pockets (optional).


  • Cut out all of the cards and laminate if desired.
  • Write a small “c” on the back of all of the curved cards and a small “s” on the back of all of the straight cards.
  • Reserve the “Curved” and “Straight” labels and and mix up the rest of the cards.
  • Sit next to your tot and explain that you are going sort the cards based on if they show a straight or a curved line.
  • Put the label that says “Curved” at the top left side of the table.  Place the “Straight” label at the top right side.  Put the rest of the cards in a pile next to you.
  • Pick up a card that shows a straight line.  Say, “This is a straight line.  A straight line takes the shortest path between two points.”  Quickly move your finger along the line and then place it under the word “Straight”.
  • Next pick up a card that contains a curved line. Slowly draw your finger along the path as you say, “This is a curved line.  A curved line does not take the shortest path between two points.”
  • Next had your tot a random card and ask if it shows a straight or curved line.   If your tot is are correct, praise her, point to the correct label and ask her to move the card there.  If your tot is incorrect, just set the card back in the pile and repeat the lesson above with two new cards.
  • Once your tot has the hang of it, invite her to finish sorting all of the cards on her own.

  • When your tot has finished sorting the cards, show her how to turn them over and check to make sure that all the cards under the “Straight” label have an “s” on the back and all of the ones under the “Curved” label have a “c”.

Observations: I was surprised by how much Sweet Pea enjoyed this activity.

It was so quick to set up and she worked until she had sorted every card in the pile.  She deliberated about each card, but the only one she got wrong was the right angle.

Even though this seems really simple, it really appeals to Sweet Pea.  She has repeated this work a couple of times since I first showed it to her.  I would recommend this activity for other tots.

Notes from the Trenches: This activity went very well.  I can’t think of anything that I would change about it.

Rating: 4 Stars * (Fun, Easy, Independent, Frugal)

Carnivals: This post is linked to One Hook Wonder’s Montessori Monday.  Visit her site to see some other great Montessori ideas.

3 comments to Intro to Geometry: Curved or Straight

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