Lesson

Remember to check back over the subtraction strategies we've seen so far.

Find the value of 58 - 29.

Worked Solution

Idea summary

We always start from the units place, when we work down our page. If we don't have enough units to subtract, we need to trade from the tens place.

What happens when we have to perform subtraction more than once? One thing we can do is use a number line to help us, as this video shows.

Find the value of 30 - 18 - 7.

Worked Solution

Idea summary

We can subtract two or more numbers by subtracting one number at a time. The second number is subtracted from the first number, and then the third number is subtracted from the result.

If we have larger numbers, we can use a vertical algorithm to solve our subtraction. Let's take a look.

Find the value of 42\,373 - 25\,215.

Worked Solution

Idea summary

We can use a vertical algorithm to subtract large numbers. This will require more steps to subtract each place value.

What happens if we have a story problem? We need to look for the keywords or clues to see what we need to do, as we see in this video.

A farmer has 83 sheep in a paddock. 9 sheep are taken away to the wool shed, and while the farmer is away 2 sheep from a neighboring farm get into the paddock through a hole in the fence.

How many sheeps are in the paddock now?

Worked Solution

Idea summary

When we solve subtraction problems, it's useful to have some different methods to use. As our numbers get larger, vertical algorithms may be necessary. Checking the answer on a calculator, or working out an estimate helps to check our answer is reasonable.

Select and apply efficient mental and written strategies and appropriate digital technologies to solve problems involving all four operations with whole numbers and make estimates for these computations

Continue and create sequences involving whole numbers, fractions and decimals. Describe the rule used to create the sequence