triangle

Everyday

1. A triangle is a flat shape with three straight sides and three corners (angles). A triangle has 3 sides. tree →
2. A triangle is a musical instrument: a metal bar bent into a triangle that you hit with a small rod. tree →
3. A triangle is anything shaped like a triangle, like a slice of pizza or a warning sign. tree →
4. A triangle can also be a group of three people or things that are linked and cause conflict, such as a love triangle. tree →

In the lessons

Maths: a shape with 3 sides; perimeter is the sum of the three sides; counting shapes, sides and corners; kinds: equilateral (all sides equal), isosceles (two equal), right-angled; the angles add to 180 degrees. Music: playing the triangle. Safety: triangle road signs warn of danger.

Examples

• A triangle has 3 sides. tree →
• Each side of the triangle is 5 cm. tree →
• She drew 6 triangles. tree →
• How many sides do 4 triangles have? tree →
• The angles of a triangle add up to 180 degrees. tree →
• He played the triangle in the school band. tree →
• Cut the sandwich into triangles. tree →
• A triangle road sign warns drivers of danger ahead. tree →
• "The swans fly in an oblique line; the cranes, in the form of a triangle; and the plovers, in a curved line like a snake." tree →

Note

Countable: a triangle, triangles. A triangle hides the number 3: sides = triangles × 3. The perimeter is the sum of the three sides. Trap: a triangle can be any size or turned any way and still be a triangle.