# 1.OA.A.2

Solve word problems that call for addition of three whole numbers whose sum is less than or equal to 20, e.g., by using objects, drawings, and equations with a symbol for the unknown number to represent the problem.

## Summary:

This standard focuses on a student’s ability to add three numbers using a variety of strategies including modeling, drawing and representing the problem with a number sentence. These word problems would require students to add three addends with a sum of no more than 20. Additionally, students can solve for any unknown portion in a problem.

## Understanding the Standard:

• Students need practice with a variety of strategies that will allow them to group addends many different ways to make the addition process easier. For instance, students should be guided to look for places where they can "make 10" before adding.
• When students are comfortable with adding three addends, begin to introduce an unknown portion in the numeric sentence. From here, students can use their knowledge of related addition and subtraction facts to solve for the unknown portion.
• The use of manipulatives, pictures, models, and technologies should be incorporated into the learning experience for greater understanding.
• Provide students with multiple opportunities to discuss their reasoning for the method they chose for their problem-solving.

## Questions to Focus Instruction:

• Can students group addends in a variety of ways to help them when adding 3 addends together?
• How can the use of manipulatives, and other visual or concrete aids, help students with their understanding of adding three addends?
• Can students employ their knowledge of related addition and subtraction facts when solving for an unknown portion?
• Can students solve problems with three addends when presented in the context of word problems?

## Skills

Prior to: Students can fluently solve simple addition and subtraction problems through 10. Students can solve word problems involving addition with two numbers.

At Grade Level: Students will master the ability to add together 3 numbers whose sum is no more than 20 in the context of word problems. Additionally, if one of the addends is unknown, students are able to find the unknown quantity using a variety of strategies.

Moving Beyond:
Students will build on their previous knowledge to solve addition problems involving three addends that requires regrouping. Students will solve problems involving the addition of three addends in two-digit numbers.