A shape can be described by counting its straight sides, which are line segments joined at corners: triangles have 3, quadrilaterals have 4, pentagons have 5, and hexagons have 6. The number of sides remains the same when a shape is rotated, resized, or shown in a different orientation; curved boundaries are not counted as straight sides. Formal angle measurement and classification of more complex polygons are beyond this understanding.
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Detailed Explanation: Describe shapes by sides
Look at the outside edge of the shape.
- Count only the straight sides.
- Touch each side as you count it once.
- Match the number of sides to the shape name:
- sides: triangle
- sides: quadrilateral
- sides: pentagon
- sides: hexagon
Example
A shape is turned sideways. Starting at the top, count its straight sides:
- 1 side
- 2 sides
- 3 sides
- 4 sides
- 5 sides
It has straight sides, so it is a pentagon.
Turning or resizing the shape does not change the number of sides. If part of the edge is curved, do not count the curved part as a straight side.
Learn by doing: Describe shapes by sides
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Practice:
Count Sides on 2D Shapes
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Download/Modify Free Grade 1 'Describe shapes by sides' Worksheet
Print this free 'Describe shapes by sides' worksheet to practice this skill away from the computer. Click 'Modify' to easily customize this worksheet to your exact needs.
This Worksheet Includes:
- Count Sides on 2D Shapes
- Classifying Polygons by Sides
- 2D Shapes by Side Count
- Classifying Polygons by Sides - Reversed
- Classifying Polygons by Sides (Real World)
- Polygons - Number of Sides to Name - First Time
- Polygons - Name to Number of Sides
- Count Sides on 2D Shapes - First Time
Units Teaching This Skill
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