Multiplying by Multiples of 10 Using Unit Form
Multiplying by Multiples of 10 Using Unit Form is a Grade 3 math skill from Eureka Math using unit form to simplify multiplication by multiples of 10. The rule is n × (m tens) = (n × m) tens. For example, 4 × 30 = 4 × (3 tens) = (4 × 3) tens = 12 tens = 120. Students first compute the basic fact (4 × 3), then apply the unit of tens. This method connects place value knowledge to multiplication and builds mental math fluency for multi-digit multiplication encountered in later grades.
Key Concepts
To multiply a number by a multiple of 10, you can multiply the basic fact and then apply the unit of tens. $$n \times (m \text{ tens}) = (n \times m) \text{ tens}$$.
Common Questions
What is the unit form strategy for multiplying by multiples of 10?
Express the multiple of 10 in unit form (e.g., 30 = 3 tens). Multiply: n × (m tens) = (n × m) tens. Convert the result back to standard form.
Use unit form to find 7 × 50.
50 = 5 tens. So 7 × 5 tens = (7 × 5) tens = 35 tens = 350.
What basic fact do you multiply when using this strategy?
Multiply the single-digit factor by the tens digit (not the full multiple of 10). Then apply the tens unit. For 6 × 40: basic fact is 6 × 4 = 24, so result is 24 tens = 240.
Why does this unit form strategy give a correct answer?
Because 40 = 4 × 10, and multiplication is associative: 6 × 40 = 6 × (4 × 10) = (6 × 4) × 10 = 24 × 10 = 240. The unit form method applies this property systematically.
In which textbook is Multiplying by Multiples of 10 Using Unit Form taught?
This skill is taught in Eureka Math, Grade 3.