Lesson

Do you remember how to solve addition problems by writing them down the page, using an algorithm ?

Find the value of 41 + 56.

Worked Solution

Idea summary

You might notice that sometimes the standard algorithm is called the 'vertical algorithm'. Let's think about why. When we use the standard algorithm, we line our numbers up in 'vertical' place value columns.

Sometimes when we add numbers together we need to regroup, or use trading. Let's see when we need to do this, and how we do it.

Find the value of 19 + 25.

Worked Solution

Idea summary

The largest value a digit can be is 9. If we add and end up with more than 9, we need to trade, or regroup, to the next digit to the left.

uses mental and written strategies for addition and subtraction involving two-, three-, four and five-digit numbers