Decimals - Add and Subtract Decimals with Different Decimal Places - Presentation

The interactive lesson on adding and subtracting decimals with different decimal places starts with a focus on fluency and reasoning. Students are encouraged to discuss and reflect on what they need to remember when working with calculations involving decimals that are not aligned. The lesson includes a series of activities where students are presented with word problems to apply their decimal knowledge. For example, in one activity, Malachi is swimming laps and has covered a distance of 12.023km with 2.8km more to go. Students are tasked with determining the total distance Malachi will swim, which involves adding the two distances together.

Key to the lesson is the emphasis on correctly aligning numbers according to their place value when performing calculations. Students are shown how to line up the decimals and are given the option to use zero as a placeholder to ensure accurate addition or subtraction. In another activity, Malachi has to swim a total of 14.801km and has already completed 6.34km. Students must figure out the remaining distance he needs to swim, which requires a subtraction calculation. The lesson guides students through the correct method to perform this calculation, highlighting the importance of decimal place alignment to arrive at the correct answer. Finally, students are given independent work to practise solving word problems that involve adding and subtracting decimals with different decimal places.