Triangles, Rectangles, Squares, and Circles
Grade 4 students identify and draw triangles, rectangles, squares, and circles in Saxon Math Intermediate 4, focusing on defining properties of each shape. A circle is defined as a closed curve where every point on the edge is the same distance from the center. Key vocabulary includes center, radius (half the distance across), and diameter (full distance across the center, always double the radius). Students apply the formula d = 2 × r: a circle with radius 4 cm has diameter 8 cm.
Key Concepts
New Concept A circle is a closed, curved shape in which all points on the shape are the same distance from the center.
What’s next Next, you’ll practice drawing these basic shapes and explore their key properties, such as radius and diameter.
Common Questions
What is the definition of a circle in Grade 4 math?
A circle is a closed curved shape where every single point on the edge is exactly the same distance from the center. This equal distance property is what distinguishes a circle from other rounded shapes.
What is the difference between radius and diameter?
The radius is the distance from the center of a circle to any point on its edge—halfway across. The diameter is the distance all the way across the circle through the center. The diameter is always exactly twice the radius: d = 2r.
How do you find the diameter if you know the radius?
Multiply the radius by 2. If a circle has a radius of 4 cm, then its diameter is 2 × 4 = 8 cm. The diameter is always twice as long as the radius.
How do you find the radius if you know the diameter?
Divide the diameter by 2. If a circle has a diameter of 16 inches, then its radius is 16 ÷ 2 = 8 inches.
What properties define a rectangle?
A rectangle has four sides with four right angles (90 degrees). Opposite sides are equal in length. A square is a special rectangle where all four sides are equal.
How are triangles classified in Grade 4?
Triangles are classified by their angles (acute, right, obtuse) or by their sides (equilateral with 3 equal sides, isosceles with 2 equal sides, scalene with no equal sides).