Maryland Math 6.NOS.B.3.a

Math6th GradeNumber and Operation Sense

The Standard

6.NOS.B.3: Fluently multiply and divide multi-digit decimals to the thousandths in context.

Extend estimation strategies to estimate and assess the reasonableness of products and quotients.

Maryland College and Career Ready Standards for Mathematics (2025) · COMPUTE FLUENTLY WITH MULTI-DIGIT NUMBERS AND FIND COMMON FACTORS AND MULTIPLES.

Teacher's field guide

What Students Need to Do: Students round numbers or choose nearby numbers that are easy to multiply or divide. They use the estimate to decide whether a calculated answer makes sense.
What Mastery Looks Like: A student estimates 398 × 21 as 400 × 20, or about 8,000. They can explain why 80,000 is too large.
Common Misconceptions: Students may accept 80,000 for 398 × 21 because they lose track of place value. Some treat an estimate as an exact answer.
How to Assess It: Exit ticket: Estimate 1,197 ÷ 29 using nearby easy numbers. Is 400 a reasonable quotient? Show your estimate and explain.

Lesson moves

Give pairs cards labeled 398, 21, 8,000, and 80,000; they choose the plausible estimate and write the rounding that supports it.
Ask students to write two sentences explaining whether 1,197 ÷ 29 could equal 400, using 1,200 ÷ 30 to support their answer.
Play Estimate and Check: show 48 × 203 with choices 974, 9,744, and 97,440; partners pick the plausible answer and explain.
Use a grocery flyer price of $6.89 for one case of water to estimate the cost of 19 cases before multiplying exactly.

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