• Mastery PD Materials

Multiplication: partitioning leading to short multiplication

Spine 2: Multiplication and Division – Topic 2.14

Introduction

Introduce the short multiplication algorithm, using it to multiply two-/three-digit numbers by single-digit numbers; explore regrouping where necessary.

Teaching points

  • Teaching point 1: The distributive law can be applied to multiply any two-digit number by a single-digit number, by partitioning the two-digit number into tens and ones, multiplying the parts by the single-digit number, then adding the partial products.
     
  • Teaching point 2: Any two-digit number can be multiplied by a single-digit number using an algorithm called ‘short multiplication’; the digits of the factors must be aligned correctly; the algorithm is applied working from the least significant digit (on the right) to the most significant digit (on the left); if the product in any column is ten or greater, we must ‘regroup’.
     
  • Teaching point 3: The distributive law can be applied to multiply any three-digit number by a single-digit number, by partitioning the three-digit number into hundreds, tens and ones, multiplying the parts by the single-digit number, then adding the partial products.
     
  • Teaching point 4: Any three-digit number can be multiplied by a single-digit number using the short multiplication algorithm.

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