Triangle
A triangle is a closed two-dimensional shape with three straight sides and three angles. The sum of the angles in a triangle is always 180 degrees. Triangles are classified based on the length of their sides and the measure of their angles.
Types of Triangles
1. By Side Length:
- Equilateral Triangle: All three sides are of equal length.
- Isosceles Triangle: Two sides are of equal length.
- Scalene Triangle: All three sides have different lengths.
2. By Angle Measure:
- Acute Triangle: All angles are less than 90 degrees.
- Right Triangle: One angle is exactly 90 degrees.
- Obtuse Triangle: One angle is greater than 90 degrees.
Properties of Triangles
1. Sum of Angles: The sum of the three interior angles in a triangle is always 180 degrees.
2. Side Lengths: In a triangle, the sum of the lengths of any two sides must be greater than the length of the third side.
3. Area: The area of a triangle can be calculated using the formula: Area = (base * height) / 2.
Understanding the different types and properties of triangles is important in geometry and various real-world applications.
.◂Math Worksheets and Study Guides Third Grade. Double Digit Addition
Study Guide
Double Digit Addition 
Worksheet/Answer key
Double Digit Addition Worksheet/Answer key
Double Digit Addition Worksheet/Answer key
Double Digit Addition Worksheet/Answer key
Double-Digit Addition
Worksheet/Answer keyWorksheet/Answer keyWorksheet/Answer keyWorksheet/Answer keyThe resources above cover the following skills:
Number and Operations (NCTM)
Compute fluently and make reasonable estimates.
Develop fluency in adding, subtracting, multiplying, and dividing whole numbers.
Select appropriate methods and tools for computing with whole numbers from among mental computation, estimation, calculators, and paper and pencil according to the context and nature of the computation and use the selected method or tools.
Algebra (NCTM)
Use mathematical models to represent and understand quantitative relationships.
Model problem situations with objects and use representations such as graphs, tables, and equations to draw conclusions.
Connections to the Grade 3 Focal Points (NCTM)
Number and Operations: Building on their work in grade 2, students extend their understanding of place value to numbers up to 10,000 in various contexts. Students also apply this understanding to the task of representing numbers in different equivalent forms (e.g., expanded notation). They develop their understanding of numbers by building their facility with mental computation (addition and subtraction in special cases, such as 2,500 + 6,000 and 9,000 - 5,000), by using computational estimation, and by performing paper-and-pencil computations.