CK-12 Foundation
Ck 12: Elem Math: Fact Families Numbers to 1000
[Free Registration/Login may be required to access all resource tools.] The video shows how to determine the missing number sentence when adding and subtracting 3-digit numbers by using fact families.
Khan Academy
Khan Academy: Add and Subtract on a Number Line
Practice adding and subtracting numbers like 554 and 237 using a number line. All numbers are less than 1000. Students receive immediate feedback and have the opportunity to try questions repeatedly, watch a video or receive hints.
Illustrative Mathematics
Illustrative Mathematics: Using Operations and Parentheses
The purpose of this task is to give students a chance to work creatively with three of the four fundamental arithmetic operations (addition, subtraction, and multiplication). It is well suited for helping students develop fluency with...
Illustrative Mathematics
Illustrative Mathematics: 4.nbt What's My Number?
The purpose of this task is for students to reason about base-ten numbers on the number line in a way that will require them to use what they know about place value. Students first represent addition and subtraction on the number line in...
Shmoop University
Shmoop: Fractions & Decimals: Adding & Subtracting Decimals
The mathematics notes investigate how to add and subtract decimals. Examples and practice problems with solutions are included.