2. Addition and subtraction

Lesson

Do you remember how we can round numbers, to help us simplify some number problems?

Round $3322$3322 to the nearest thousand.

When we solve addition and subtraction problems, estimating our answer gives us an idea of what to expect. In this video, we see how we can estimate the answer to addition or subtraction problems, using a number line to help us.

We want to estimate the answer to $258-26$258−26.

Round each of the two numbers to the nearest $10$10:

$258-26$258−26 is rounded to $\editable{}-\editable{}$− $=$=$\editable{}$ Find the value of $258-26$258−26.

How can we solve a problem with more than one part? Have a look at this video to see some different ways to do this.

Find the value of $570+25+4$570+25+4.

Remember!

By adding in a different order, we may be able to use strategies such as Bridge to $10$10, to help us solve a problem. The number lines below show how we can solve $8+4+3$8+4+3 by changing the order, and still arrive at the same answer of $15$15.

Apply place value to partition, rearrange and regroup numbers to at least tens of thousands to assist calculations and solve problems

Use equivalent number sentences involving addition and subtraction to find unknown quantities