Maryland Math 4.NOS.B.5.a
The Standard
- 4.NOS.B.5
- Multiply a whole number of up to four digits by a one-digit whole number, and multiply two two-digit numbers.
Apply estimation strategies to estimate products.
Maryland College and Career Ready Standards for Mathematics (2025) · USE PLACE VALUE UNDERSTANDING AND PROPERTIES OF OPERATIONS TO PERFORM MULTI-DIGIT ARITHMETIC.
Teacher's field guide
What This Standard Means
What Students Need to Do
- Students round factors to nearby tens or hundreds, then multiply to estimate a product. They explain why their chosen numbers give a reasonable estimate.
What Mastery Looks Like
- A student can estimate 48 × 21 as 50 × 20 = 1,000 without finding the exact product. They can explain why 50 and 20 are good choices.
Common Misconceptions
- Students may round 48 to 40, forget that 50 × 20 is 1,000, or call the estimate the exact product. Some choose easy numbers that are too far from the original factors.
How to Assess It
- Exit ticket: Estimate 48 × 21 without finding the exact product. Show the numbers you used and explain why they make sense.
Lesson moves
Ways to Teach It
Give pairs cards labeled 48 and 21 and number lines marked by tens; have them place each card, round, and multiply.
Ask: Which gives a closer estimate for 398 × 6, 400 × 6 or 300 × 6? Why?
In pairs, draw two two-digit number cards, round both numbers, and race to find an estimated product.
Show an order of 48 notebooks at $21 each and ask students to estimate the total cost.
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Printable 4.NOS.B.5.a Worksheet
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Related Standards
- 4.NOS.B.3.a
Apply estimation strategies to estimate sums and differences.
- 6.NOS.B.3.a
Extend estimation strategies to estimate and assess the reasonableness of products and quotients.
- 5.NOS.B.4.a
Apply estimation strategies to estimate products.
- 5.NOS.B.7.a
Apply estimation strategies to estimate products and quotients.
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