In this Grade 5 lesson from Illustrative Mathematics Chapter 5, students learn to add decimals to the hundredths place using the standard algorithm with correct place value alignment. The lesson focuses on a common error in which decimal numbers are right-aligned like whole numbers, causing digits of different place values — such as tenths and hundredths — to be added together incorrectly. Students identify and correct these alignment mistakes, reinforcing that decimal numbers must be lined up by place value, not by their rightmost digit.
Section 1
Application: Approximate vs. Exact Quantities
Most conversions between customary and metric systems are approximate (), meaning they are rounded. An exact conversion () is a defined relationship. The primary exact conversion between systems is for inches and centimeters.
Section 2
Context and Measurement Precision
The precision of a measurement is limited by the measuring tool. The context of a situation determines the necessary level of precision, which is how detailed a measurement needs to be to be useful.
Expand to review the lesson summary and core properties.
Section 1
Application: Approximate vs. Exact Quantities
Most conversions between customary and metric systems are approximate (), meaning they are rounded. An exact conversion () is a defined relationship. The primary exact conversion between systems is for inches and centimeters.
Section 2
Context and Measurement Precision
The precision of a measurement is limited by the measuring tool. The context of a situation determines the necessary level of precision, which is how detailed a measurement needs to be to be useful.