Subtraction, Take Away, Minus, Difference!

0

Posted by saratat | Posted in Uncategorized | Posted on October 14, 2016

Yes, we are working on subtraction once again in 1/2ST. We are developing and consolidating strategies to support our ability to solve subtraction problems.

Other words for subtraction include:

  • subtraction
  • take away
  • minus
  • difference

Some of the strategies we have been practising in our ‘Just Right’ Maths groups include:

  • counting back on a number line

subtraction_countback-strategy

  • counting back in our heads. For example, if we had 10 – 3, we would count back from 10 3 times: 9, 8, 7! The number we land on is the answer. So the answer is 7!
  • counting back using our fingers

subtraction_count-back-using-fingers

  • using doubles facts, to know our halves facts.
    For example, if:
    4 + 4 = 8, then
    8 – 4 = 4!
  • using friends of 10 and fact families.
    For example, if 6 + 4 = 10, then
    10 – 6 = 4, or
    10 – 4 = 6
  • And regrouping. 
    For example,
    3  1
    -1  2
    –––––

    Start in the ones column.
    If the digit on top is smaller than the digit on the bottom then you need to regroup!

    Take 1 ten and regroup it to 10 ones

        2   11
    –   1    2
    –––––
        1    9

    Then you can say,
    11 ones  –  2 ones  = 9 ones and
    2 tens    –  1  ten    = 1 ten.

    So the answer is, 19!

Write a comment

Subscribe

Follow this blog

Get every new post delivered right to your inbox.

Skip to toolbar