Ratios and Proportion · B5 Mathematics

Lesson notes

Learning Objectives

Indicator: B5.1.4.1.4 - Use models to explain the result of addition and subtraction of decimals (up to the thousandths)

By the end of the lesson, learners can:

Use decimal grids and base-ten blocks to model the addition of decimals up to the thousandths place and explain the result.
Use decimal grids and base-ten blocks to model the subtraction of decimals up to the thousandths place and explain the result.
Line up decimal points correctly before adding or subtracting decimals with different numbers of decimal places.
Justify their answers by explaining how regrouping (carrying and borrowing) works when adding and subtracting decimals.
Solve real-life problems involving addition and subtraction of decimals using models and written methods.

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Curriculum details

Strand: Number (Strand 1)
Sub-strand: Ratios and Proportion (1.4)
Content standard: B5.1.4.1 - Demonstrate understanding of decimals fractions and strategies for comparing, adding and subtracting decimal fraction
Indicator: B5.1.4.1.4 - Use models to explain the result of addition and subtraction of decimals (up to the thousandths)
Suggested placement: Term 2, Week 4 (Week 16 of the year)
Our suggestion, laid out in curriculum order across three terms of twelve weeks. NaCCA does not fix the week, so follow your school's scheme of learning.
Curriculum reference: Mathematics Curriculum for Primary Schools (Basic 4-6), 2019, p. 80
Transcribed from the official NaCCA publication. Check this page against the source.

Exemplars (from the NaCCA curriculum)

E.g. 1 To add 0.645 and 0.39, means sum + which is = = 1.035. That is, since
1000 100 1000 1000
one is hundredths and other thousandths (i.e. one has 2 decimal places and the other 3 decimal places) we can line up the decimal points to align the place values and add as whole numbers
E.g. 2 To subtract 0.395 from 0.6 and, one number is in tenths and other is in thousandths (i.e. one has 1 decimal place and the other 3 decimal places) it is important to line up the decimal points to align the place values and add as whole numbers.