Repeated Addition
Repeated addition as a model for decimal multiplication is a Grade 5 math skill in enVision Mathematics, Chapter 4: Use Models and Strategies to Multiply Decimals. When multiplying a decimal by a whole number n, students can think of it as adding the decimal n times. This connects multiplication to its additive foundation and helps verify decimal products.
Key Concepts
Multiplication of a decimal by a whole number can be represented as repeated addition. The whole number, $n$, tells you how many times to add the decimal, $d$.
$$n \times d = \underbrace{d + d + \dots + d} {n \text{ times}}$$.
Common Questions
How does repeated addition relate to multiplying a decimal by a whole number?
Multiplying a decimal by a whole number n means adding that decimal n times. For example, 4 x 0.3 = 0.3 + 0.3 + 0.3 + 0.3 = 1.2.
What is 5 x 0.7 using repeated addition?
0.7 + 0.7 + 0.7 + 0.7 + 0.7 = 3.5. So 5 x 0.7 = 3.5.
Why is repeated addition helpful for understanding decimal multiplication?
It builds on students existing addition skills and makes the concept of multiplication concrete, showing exactly where the product comes from.
Where is repeated addition for decimals taught in enVision Grade 5?
Chapter 4: Use Models and Strategies to Multiply Decimals in enVision Mathematics, Grade 5.
Is repeated addition always efficient for decimal multiplication?
No, for large whole number factors it becomes tedious. It is best used as a conceptual tool, then students move to more efficient algorithms.