In this Grade 5 Eureka Math lesson from Chapter 7, students learn to estimate multi-digit products by rounding factors to a basic fact and applying place value patterns. They practice rounding multi-digit numbers to convenient values, then use those rounded factors alongside multiplication by multiples of 10, 100, and 1,000 to find reasonable estimates for products like 456 × 42 or 4,560 × 42. The lesson builds mental math fluency by connecting basic multiplication facts to larger place value relationships.
Section 1
Rounding to a Given Place Value
To round a number to a specific place value, look at the digit immediately to the right of that place. If the digit is 5 or greater, round up the digit in the target place value. If the digit is less than 5, keep the digit in the target place value the same. All digits to the right of the rounded place value become zero.
Section 2
Multiplying by Multiples of 10, 100, and 1,000
To multiply a whole number by a multiple of 10, 100, or 1,000, you can multiply the basic fact (the non-zero digits) and then append the total number of zeros from the factors to the product.
Section 3
Application: Solve Word Problems Using Estimation
To solve a multi-step word problem with estimation, first identify the sequence of operations needed. Next, estimate the product for each multiplication step by rounding the factors. Finally, use these estimates to perform the remaining steps and find an approximate solution.
Expand to review the lesson summary and core properties.
Section 1
Rounding to a Given Place Value
To round a number to a specific place value, look at the digit immediately to the right of that place. If the digit is 5 or greater, round up the digit in the target place value. If the digit is less than 5, keep the digit in the target place value the same. All digits to the right of the rounded place value become zero.
Section 2
Multiplying by Multiples of 10, 100, and 1,000
To multiply a whole number by a multiple of 10, 100, or 1,000, you can multiply the basic fact (the non-zero digits) and then append the total number of zeros from the factors to the product.
Section 3
Application: Solve Word Problems Using Estimation
To solve a multi-step word problem with estimation, first identify the sequence of operations needed. Next, estimate the product for each multiplication step by rounding the factors. Finally, use these estimates to perform the remaining steps and find an approximate solution.