Number
Knowing our numbers
Compare, order, round and estimate with numbers of four digits and more.
A long number is not harder than a short one — it just has more places in it. Every digit is worth ten times the digit to its right, so the digit furthest to the left is the one that decides how big the number really is. That single idea is what makes comparing, ordering and rounding straightforward.
Comparing two numbers
First count the digits: for whole numbers, more digits means a bigger number, always. If they have the same number of digits, compare them place by place from the left and stop at the first place where they disagree. That place decides it, and nothing further right can change the decision.
Have a play
Move between four thousand and five thousand, a hundred at a time. Watch which end of the line you are nearer.
Tap anywhere on the line.
Worked example
Which is larger, 45678 or 45687?
Both have five digits, so counting digits does not settle it.
A six-digit number would beat a five-digit one outright, but these are level.
Try it together
Let us estimate 4783 + 2149 by rounding each number to the nearest thousand.
An estimate is not a wrong answer — it is a quick answer you can check the real one against. Round first, then add.
1.Round 4783 to the nearest thousand.
Watch out
Rounding looks at one digit only — the one immediately to the right of the place you are rounding to. Rounding 4649 to the nearest hundred gives 4600, not 4700: the tens digit is 4, and the 9 after it has no say.
Have a go
Have a go on your own: round 3462 to the nearest hundred.
Hint: The tens digit is 6.
Ready to practise?
Eight questions on what you have just read. Nothing is timed, and you can play as many times as you like.