Learning different strategies to add and subtract numbers within 100 is a second grade, Common Core math skill: 2.NBT.5. Below we show two videos that demonstrate this standard. Then, we provide a breakdown of the specific steps in the videos to help you teach your class.
Your students should be familiar with the first grade skill of counting up to 120 starting from any number below 120 (1.NBT.1), this skill helps them understand greater or less than values. The second grade skill is also closely linked to the first grade skill of understanding place values (ones and tens) in two-digit numbers (1.NBT.2).
Comparing large numbers as greater than, less than, and equal to will help your students understand future concepts in third grade. In third grade, your students will learn how to interpret the products of whole numbers (i.e. 8 x 3 is the same as 8 groups of 3 objects each) (3.OA.1). They will also learn to use multiplication and division within 100 while solving word problems in situations that involve “equal groups, arrays, and measurement quantities” (3.OA.3).
Common Core Standard: 2.NBT.5 - Fluently add and subtract within 100 using strategies based on place value, properties of operations, and/or the relationship between addition and subtraction
Students who understand this principle can:
2 Videos to Help You Teach Common Core Standard: 2.NBT.5
Below we provide and breakdown two videos to help you teach your students this standard.
Video 1: Using Rods and Cubes to Subtract
This video shows students how to subtract using drawings. Though it only covers subtraction problems, the method can be adapted for addition problems as well.
The first problem is 92 - 34 = ?. How the video solves this problem is related below.
The second problem is 43 - 12 = ?. The video follows the same pattern as the first problem to solve the equation.
Video 2: Finding the Keys to Treasure Chests
This video covers some strategies for adding and subtracting up to 100. Boddle presents 5 treasure chests that need to be unlocked. However, they can only be opened with the correct key, and to select the correct key, one must solve the math problem.
Boddle asks students if they can help her unlock the chests.
Boddle congratulates the students on a job well done, hoping to see them next time.
Want more practice?
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