Math--Chapter 3

Chapter 3: Add and Subtract Whole Numbers

Lesson 1: Use Mental Math Strategies. Objective: To use mental math strategies to find sums and differences.

Lesson 2: Estimate Sums and Differences. Objective: To estimate sums and differences.

Lesson 3: Add and Subtract to 4-Digit Numbers. Objective: To add and subtract to 4-digit numbers.

Lesson 4: Subtract Across Zeros. Objective: To subtract whole numbers with zero and regrouping.

Lesson 5: Choose a Method. Objective: To add and subtract numbers with regrouping through hundred thousands.

Lesson 6: Problem Solving Strategy: Estimate or Find Exact Answers. Objective: To solve problems by deciding whether to estimate or find exact answers.


Vocabulary: sum, difference, estimate, round

sum: the answer to an addition problem

difference: the answer to a subtraction problem

estimate: to find an answer close to an exact answer

round: to replace a number with another number that tells about how many or how much


Rounding Help:

Rounding Rap

Mark the place. Look to the right. 4 or less are out of sight. 5 and up will buy one more before they too are out the door. In those empty right-hand spaces, zeros keep the proper places.

Estimating and rounding:

Rounding Whole Numbers:

Our textbook website:


Some good practice websites: