Maryland Math 5.NOS.B.4.a

Math5th GradeNumber and Operation Sense

The Standard

Apply estimation strategies to estimate products.

Maryland College and Career Ready Standards for Mathematics (2025) · PERFORM OPERATIONS ON MULTI-DIGIT WHOLE NUMBERS AND WITH DECIMALS TO HUNDREDTHS.

Teacher's field guide

What Students Need to Do: Students round factors or choose nearby numbers that are easy to multiply. They use place value to check whether their estimate makes sense for whole numbers and decimals.
What Mastery Looks Like: For 48 × 21, a student uses 50 × 20 to estimate 1,000. For 0.48 × 39, they use 0.5 × 40 to estimate 20, not 200. They explain that each answer is an estimate.
Common Misconceptions: Students may round a factor but then multiply using the original number. They may treat 0.48 as 48 and get an estimate that is 100 times too large. Some write an estimate as if it were exact.
How to Assess It: Exit ticket: Estimate 3.87 × 19 without finding the exact product. Show the numbers you chose and explain why your answer is reasonable.

Lesson moves

Give pairs number cards labeled 48, 21, 3.87, and 19; have them pair cards, round the factors, and estimate each product.
Write 29 × 41 on the board and ask, 'Is 30 × 40 or 20 × 40 a better estimate? Why?'
Play Estimate Match with problem cards 48 × 21, 3.87 × 19, and 0.48 × 39 and answer cards 1,000, 80, and 20.
Post a price tag of $3.87 per notebook and ask students to estimate the cost of 19 notebooks.

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