Standard: 1.NBT.C4 – Add within 100, including adding a two-digit number and a one-digit number, and adding a two-digit number and a multiple of 10, using concrete models or drawings and strategies based on place value, properties of operations, and/or the relationship between addition and subtraction; relate the strategy to a written method and explain the reasoning used. Understand that in adding two-digit numbers, one adds tens and tens, ones and ones; and sometimes it is necessary to compose a ten.
Grade level: Grade 1
Subject: Mathematics
Domain: Number & Operations in Base Ten
Teacher Overview
This standard focuses on developing students’ ability to add within 100, particularly by combining two-digit numbers with one-digit numbers or multiples of ten. This skill is crucial as it builds a foundation for more complex arithmetic operations and enhances their understanding of place value. Students need to have a solid grasp of basic addition and subtraction, understand place value, and be comfortable with single-digit arithmetic before tackling this standard.
Mastering this standard will enable students to handle more complex arithmetic operations and prepare them for future topics like multiplication and division.
Common Misconception 1
Some students might incorrectly believe that addition should always proceed from left to right, which can lead to errors in place value alignment.
Intervention 1
Use step-by-step guided practice to reinforce the correct procedure of starting from the rightmost digit (ones place) and moving left.
Common Misconception 2
Another common error is not recognizing the need to compose a ten when the sum of the ones place digits equals or exceeds ten.
Intervention 2
Incorporate hands-on activities with physical objects or visual aids to demonstrate how grouping ten ones into a ten simplifies the addition process.
Prerequisite Knowledge
Students should understand basic addition and subtraction concepts, be familiar with single-digit addition and subtraction, and have an understanding of place value (ones and tens).
Subsequent Knowledge
Students will develop skills in more complex addition and subtraction problems, including those involving regrouping, and will be prepared to tackle multiplication and division in later grades.
Instructional Activities
- Using base-ten blocks to add two-digit and one-digit numbers
- Drawing place value charts to visualize addition
- Playing math games that involve adding numbers within 100
- Working on word problems that require adding two-digit numbers
- Using number lines to demonstrate addition
