Sign In
Sign Up
flag-ie

Subtraction strategies

Topic Notes

In this lesson, we will learn:

  • The subtraction strategy of: (1) using a friendly number with adjustment, (2) adding to both numbers to create a friendly number, and (3) counting on from the first number (subtrahend)
  • Understanding subtracting by 9

Notes:

  • Method 1: change into a "friendly" number then adjust (by adding)
    • Round one the number being taken away to the nearest multiple of 10
    • Then adjust by adding how much you rounded by to get the answer
Subtraction Strategies
  • Method 2: make "friendly" numbers by adding to both numbers
    • Add to one of the numbers so that it becomes the nearest multiple of 10
    • Add the same amount to the other number
Subtraction Strategies
  • Method 3: subtracting by counting on
    • Start with the number you're taking away (the second number)
    • Then count up until you get the first number
Subtraction Strategies