Lesson objective: Understand that decimals can be rounded.

Students bring prior knowledge of rounding whole numbers from 3.NBT.A.1. This prior knowledge is extended to decimals as students round decimals. A conceptual challenge students may encounter is understanding how different place values influence how a decimal is rounded.

The concept is developed through work with a number line, which will provide a visual representation of how different decimals are related to one another and their relative distance from the place value to which they are being rounded.

This work helps students deepen their understanding of number because decimals are composed of numbers in different place values. These place values do not just represent individual digits; they determine the numerical value of a decimal.

Students engage in Mathematical Practice 7 (Look for and make use of structure) as they round decimals to a specific place value using the digit in the place value to its right.

Students engage in Mathematical Practice 6 (Attend to precision) as they decide which digit to evaluate (the one immediately to the right of the place value being rounded to) and communicate their reasoning through the use of number lines.

**Key vocabulary:**

- number line
- ones
- place value
- rounding
- tenths
- hundredths
- thousandths

**Special materials needed:**

- scratch paper with number lines, as needed