Using 10x: What is it?

In this multiplication strategy, students use their knowledge of the tens times tables and the relationship to the five times tables to solve questions.

Overview

In all grades, practice in composing and decomposing numbers into ones, tens, and sometimes hundreds will help students link these important concepts to multi digit computations. When working with 10x, It is beneficial for students to understand why they can ‘add a zero’ and have the understanding that the number is getting ten times larger. Simply teaching to just add a zero does not support deeper understanding but is rather a procedure.

Notice that after multiplying a whole number by 10, there is always a 0 in the ones place of the product. This happens because after all the digits have moved left one place you end up with 0 ones. You can extend the same thinking to multiplying by 100 and 1000. 

It may be tempting to simply give students rules about adding a zero to the end of the number when multiplying it by 10. However, it is important to focus on why adding zeros makes sense. With a firm foundation in why we add zeros, students will understand when it is appropriate to add zeros or when it isn't. For example, you don't add a 0 to the end when you multiply a decimal by 10 (4.2 x 10 = 42). 

The 10 X strategy is an essential building block as many strategies for multi digit multiplication depend on decomposing numbers into their place value to multiply by 10, 100, or 1000. This strategy will support students’ understanding of multiplying decimals and measurement conversions. It will also support students’ understanding of dividing by 10. 

Where to Next?

Once students are confident recognizing their 10x facts they can be encouraged to explore 5x as half of the x10 fact.