CCSS.Math.Content.5.NF.B.5a
The standard
Comparing the size of a product to the size of one factor on the basis of the size of the other factor, without performing the indicated multiplication.
Common Core State Standards for Mathematics
What this standard means
Students need to judge whether multiplying will make a number larger, smaller, or stay the same by looking at the other factor. They should know that multiplying by a number greater than 1 makes the product larger, by 1 stays the same, and by a number between 0 and 1 makes it smaller.
Mastery looks like explaining the comparison without calculating, using words, number lines, or simple examples. Students often get stuck because they think multiplication always makes numbers bigger. They may also confuse a fraction like 5/4 with 4/5, so ask them to compare the factor to 1 first.
Ways to teach it
- Use fraction strips to model 6 times 1/2, 6 times 1, and 6 times 3/2, then compare each product to 6.
- Prompt students to explain, without solving, whether 8 times 3/4 is greater than, less than, or equal to 8.
- Show five expressions and ask students to mark each product as bigger, smaller, or same as the whole-number factor.
- Connect to recipes by asking whether 2/3 batch of 12 muffins gives more or fewer muffins than the original recipe.
Plan a lesson for CCSS.Math.Content.5.NF.B.5a
Generate a complete lesson plan aligned to this standard, with objectives, activities, and materials. Free, no account needed.
Related standards
- CCSS.Math.Content.5.NF.B.5b
Explaining why multiplying a given number by a fraction greater than 1 results in a product greater than the given number (recognizing multiplication by whole n...
- CCSS.Math.Content.5.NF.B.5
Interpret multiplication as scaling (resizing), by:
- CCSS.Math.Content.6.RP.A.3d
Use ratio reasoning to convert measurement units; manipulate and transform units appropriately when multiplying or dividing quantities.
- CCSS.Math.Content.4.OA.A.2
Multiply or divide to solve word problems involving multiplicative comparison, e.g., by using drawings and equations with a symbol for the unknown number to rep...