NumberNut
Number Nut: More Than Two Addends
Develop strategies for adding more than two addends with this quick addition lesson. Examine how grouping numbers can help make adding multiple numbers easier. Then, practice your new skills using the related interactive games that are...
Teaching Treasures Publications
Teaching Treasures: Year Two Timed Mental Math (Page 3)
Increase your addition and subtraction speed using this timed interactive worksheet. With just ten problems and five minutes, this worksheet is suitable for practice or as an assessment tool. Check your answers immediately.
Lawrence Hall of Science
The Math Page: Skill in Arithmetic: The Meaning of Subtraction, and Mental Calculation
This website explains and defines basic subtraction. There are practice problems at the very end of this lesson.
Homeschool Math
Homeschool Math: Adding and Subtracting Decimals With Two Decimal Digits
This is a complete lesson with instruction, word problems, and exercises about adding and subtracting decimals with two decimal digits (hundredths).
CK-12 Foundation
Ck 12: Elem Math: Adding and Subtracting Three or More Numbers
[Free Registration/Login may be required to access all resource tools.] This is a set of practice problems where students are given word problems where they have to add or subtract 3 or more 1-digit numbers.