Maryland Math 6.NOS.B.3.d

Math6th GradeNumber and Operation Sense

The Standard

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

Determine and explain when a strategy or algorithm is most efficient.

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 solve multi-digit problems using more than one method. They choose the method that takes fewer steps or makes errors less likely, and explain their choice.
What Mastery Looks Like: A student sees that 48 × 25 is easier as 12 × 100 than with a written algorithm. They can show both methods, get 1,200, and explain why the first is quicker.
Common Misconceptions: Students may assume the written algorithm is always fastest. When using 100 × 47 to find 99 × 47, they may forget to subtract one group of 47.
How to Assess It: Exit ticket: Solve 48 × 25 two ways. Circle the method you would use next time and explain what makes it quicker.

Lesson moves

Give pairs of students problem cards for 48 × 25, 99 × 47, and 36 × 47; have them sort by useful method and solve.
Ask students to write how they would find 99 × 47 without a written algorithm, then compare the number of steps.
Play strategy match: pairs draw a multiplication card, choose a method, solve, and earn a point for a correct explanation.
Ask how to find the pencils in 25 boxes of 24, then compare 24 × 100 ÷ 4 with written multiplication.

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