Triangles

Age
6-9.

Materials

 * Reading labels - "scalene triangle", "isosceles triangle", "equilateral triangle", "right-angled triangle", "obtuse- angled triangle", "acute-angled triangle"

Presentation

 * 1) Take out the first triangle in the first row.
 * 2) Invite the child to identify the three sides and observe whether the sides are alike or different.
 * 3) All three sides are different, this is a scalene triangle.
 * 4) Relate the story of the farmer and the ladder he used to pick fruit from his trees.
 * 5) Unlike the ladders we use today, the rungs of this ladder were all different lengths.
 * 6) These ladders are still used today in lesser developed countries.
 * 7) Just as all the rungs are different lengths, the sides of this triangle are all different lengths (scalene: Latin scala, usually plural scalae - ladder, flight of steps or Greek: skalenas - limping, uneven).
 * 8) Isolate the second triangle in the first row.
 * 9) Invite the child to carefully observe its sides - two are alike.
 * 10) This is an isosceles triangle (isosceles: Greek isos - equal, and sceles - legs; thus having equal legs).
 * 11) Here it means two equal legs, or sides.
 * 12) Isolate the third triangle.
 * 13) By observing and turning the inset in its frame, the child sees that all of the sides are the same.
 * 14) This is an equilateral triangle (equilateral: Latin aequus - equal, and latus, lateris - a side; thus having equal sides).
 * 15) Place the three insets on the table and do a three period lesson.
 * 16) Isolate the first triangle in the second row.
 * 17) Identify the right angle.
 * 18) This is a right angle, it is erect.
 * 19) This is a right-angled triangle.
 * 20) How many right angles does it have? Only one.
 * 21) Isolate the second triangle.
 * 22) Identify the obtuse angle.
 * 23) Obtuse means dull.
 * 24) This is an obtuse-angled triangle.
 * 25) Count the obtuse angles... only one.
 * 26) Isolate the third triangle.
 * 27) All of these angles are smaller than the right angle.
 * 28) They are acute angles.
 * 29) Acute means sharp, pointed.
 * 30) Feel how it is sharper than the right or obtuse angles.
 * 31) This is an acute-angled triangle.
 * 32) How many acute angles does it have? Three.
 * 33) Bring out the three triangles and review the first period.
 * 34) The triangle must have one right angle to be a right-angled triangle... and so on.
 * 35) Second and third periods follow.
 * 36) Give the child the reading labels.