Subtraction is the process of finding the difference between two numbers. It is the opposite of addition. When you subtract one number from another, you are finding out how much is left after taking away a certain amount.

In written form, subtraction is often represented using the minus sign (-). For example, the subtraction of 5 from 8 can be written as 8 - 5.

Here are some important facts to remember about subtraction:

- Subtraction is not commutative, which means that the order of the numbers matters. For example, 8 - 5 is not the same as 5 - 8.
- When subtracting a smaller number from a larger number, the result is always less than the original number.
- Subtraction is the inverse operation of addition, so it undoes the effects of addition. For example, if you add 5 to a number and then subtract 5 from the result, you will get back to the original number.

There are several strategies for performing subtraction, including:

- Counting Back: Start with the larger number and count back by the value of the smaller number.
- Using Number Line: Plot both numbers on a number line and find the distance between them.
- Regrouping: When the digit in the subtrahend is larger than the corresponding digit in the minuend, regroup to borrow from the next place value.

Now that you understand the basics of subtraction, it's time to practice! Here are some problems to try:

- 12 - 7 = ?
- 25 - 13 = ?
- 48 - 29 = ?

Remember to use the subtraction strategies we discussed to help you solve these problems!

Study GuideSimilarity and scale Worksheet/Answer key

Similarity and scale Worksheet/Answer key

Similarity and scale Worksheet/Answer key

Similarity and scale Worksheet/Answer keyUsing Similar Polygons Worksheet/Answer keySimilar Polygons Worksheet/Answer keyUsing Similar Polygons Worksheet/Answer keySimilar Polygons

Number and Operations (NCTM)

Understand numbers, ways of representing numbers, relationships among numbers, and number systems.

Understand and use ratios and proportions to represent quantitative relationships.

Compute fluently and make reasonable estimates.

Develop, analyze, and explain methods for solving problems involving proportions, such as scaling and finding equivalent ratios.

Geometry (NCTM)

Analyze characteristics and properties of two- and three-dimensional geometric shapes and develop mathematical arguments about geometric relationships.

Understand relationships among the angles, side lengths, perimeters, areas, and volumes of similar objects.

Create and critique inductive and deductive arguments concerning geometric ideas and relationships, such as congruence, similarity, and the Pythagorean relationship.

Apply transformations and use symmetry to analyze mathematical situations.

Describe sizes, positions, and orientations of shapes under informal transformations such as flips, turns, slides, and scaling.

Measurement (NCTM)

Apply appropriate techniques, tools, and formulas to determine measurements.

Solve problems involving scale factors, using ratio and proportion.

Grade 8 Curriculum Focal Points (NCTM)

Geometry and Measurement: Analyzing two- and three-dimensional space and figures by using distance and angle

Students use fundamental facts about distance and angles to describe and analyze figures and situations in two- and three-dimensional space and to solve problems, including those with multiple steps. They prove that particular configurations of lines give rise to similar triangles because of the congruent angles created when a transversal cuts parallel lines. Students apply this reasoning about similar triangles to solve a variety of problems, including those that ask them to find heights and distances. They use facts about the angles that are created when a transversal cuts parallel lines to explain why the sum of the measures of the angles in a triangle is 180 degrees, and they apply this fact about triangles to find unknown measures of angles. Students explain why the Pythagorean Theorem is valid by using a variety of methods - for example, by decomposing a square in two different ways. They apply the Pythagorean Theorem to find distances between points in the Cartesian coordinate plane to measure lengths and analyze polygons and polyhedra.