# 4th Grade - Equilateral, Isosceles And Scalene Triangles

 Grade Level: 4th Skill: Shapes and Geometry Topic: Equilateral, Isosceles and Scalene Triangles Goal: Know the definitions of different triangles (i.e. equilateral, isosceles, scalene) and identify their attributes. Skill Description: Describe and identify the three types of triangles (equilateral, isosceles, and scalene).

## Building Blocks/Prerequisites

### Sample Problems

 (1) Classify the triangle. _____________ (equilateral) (2) Classify each triangle by the length of its sides: 8 cm, 6 cm, 3 cm _______________ (scalene) (3) Find the perimeter of the triangle and classify Perimeter: _______ Type of triangle: ______________ (P= 14 in.; Isosceles) (4) Use an interactive ruler to measure the triangle, then classify: ________ cm Type of triangle: __________ (scalene; measurement depends on type of ruler) (5) The lengths of my sides are: 5 in., 12 in., 12 in. What type of triangle am I? __________ (Isosceles)

### Learning Tips

 (1) Math Vocabulary Equilateral triangle- a triangle with 3 sides congruent Isosceles triangle- a triangle with two sides congruent Scalene triangle- a triangle with no sides congruent Congruent- having the same size and shape Perimeter- the distance around a figure (2) Review how to measure lines (or items) using a ruler: Most kids begin the measurement at 1 on the ruler. Remind them to start at the tip of the ruler. Practice measuring various lines and remember to write the unit (cm, m, in. etc.) at the end. (3) Review Perimeter The formula to calculate the perimeter for triangles is (Perimeter = a + b + c) (4) Tangrams Use tangrams that have the various types of triangles and sort them on a construction paper mat that has a chart for scalene, equilateral, and isosceles triangles. (5) Identify triangles Have the child look around the house and find objects that have triangular shapes. Invite them to play a game of naming the types of triangles that they find.

### Extra Help Problems

 (1) Classify the triangle __________ (Equilateral) (2) Classify the triangle _______________ (Scalene) (3) Classify the triangle ________________ (Isosceles) (4) Classify the triangle _______________ (Equilateral) (5) Classify the triangle _________________ (Scalene) (6) Classify the triangle ___________________ (Isosceles) (7) Find the perimeter. P= ______ (24m; equilateral) (8) Find the perimeter. P= ___________ (P= 19cm; scalene) (9) Find the perimeter. P= _________ (P= 18 cm; isosceles) (10) Find the perimeter. P= _________ (P= 24 in. ; scalene) (11) Find the perimeter. P = __________ (18 cm; equilateral) (12) Use an interactive ruler and measure the sides. Classify the triangle. (scalene) (13) Use an interactive ruler and measure the sides. Classify the triangle. (isosceles) (14) Use an interactive ruler and measure the sides. Classify the triangle. (equilateral) (15) Use an interactive ruler and measure the sides. Classify the triangle (isosceles) (16) If I am an isosceles triangle, what will be the length of my third side: 13 cm, 9 cm, ____cm 17 cm 9 cm 13 cm b or c (d) (17) If I am an equilateral triangle, what will be the length of my third side: 18 ft., 18 ft., _____ (a) 12 ft. (b) 18 ft. (c) 4 ft. (b) (18) If I am a scalene triangle, what will be the length of my third side: 14 in., 13, in., ____ in. (a) 14 in. (b) 13 in. (c) 17 in. (c) (19) If I have two congruent sides, what triangle am I? (Isosceles) (20) If I have three congruent sides, what triangle am I? (equilateral) (21) If I have 3 acute angles, what triangle am I? (equilateral) (22) Explain congruent sides: _________________ (all sides are equal) (23) Describe an equilateral triangle:__________ (a triangle with 3 equal (congruent) sides) (24) Describe an isosceles triangle: ___________ (a triangle with 2 equal (congruent) sides) (25) Describe a scalene triangle. (a triangle with no equal (congruent) sides)