Decimals - Rounding Decimals Activity - Presentation

In Lesson 8, titled "Round Decimals," students are introduced to the concept of rounding decimal numbers to the nearest whole number. The lesson begins with a discussion on the significance of the tenths place when rounding decimals. For example, students explore whether 2.6 should be rounded down to 2 or up to 3, and similarly, whether 5.3 rounds down to 5 or up to 6. This encourages students to think critically about the rounding process. The lesson utilises a number line marked in intervals of 10s to visually aid understanding. Students are prompted to estimate where numbers such as 65 and 1239 would fall on this line, with an emphasis on the importance of identifying the halfway points between each interval of ten.

Further activities guide students to accurately place numbers on the number line and to round them to the nearest 10. For example, they learn that 39 is closer to 40 than to 30, and therefore, when rounded, 39 becomes 40. The lesson also includes an activity with digit cards, where students create various decimal numbers and then estimate their positions on a number line with intervals of ones. This activity reinforces the concept of tenths and how they influence rounding decisions. For instance, a number like 3.9, which is just one-tenth less than 4, would be placed close to 4 on the number line. The lesson concludes with an emphasis on the role of tenths in determining which integer a decimal is closest to, enabling students to write complete sentences that describe the rounding process for various decimal numbers.