Big numbers in pieces
You learn to split big numbers into pieces, to write them or find the value of a digit.
How to work it out
- Cut a number word into pieces, or a number into groups of three digits.
- Write each piece of a word as a number, and add the pieces.
- To find the value of a digit, find its place by counting from the right.
- Multiply the digit by the value of that place.
A worked example
three thousand four hundred and eight
- Cut the word into pieces: three thousand, four hundred, eight.
- Write each piece as a number: 3,000, 400 and 8.
- Add: 3,000 + 400 + 8 = 3,408.
More examples
five hundred and eighty
- Cut the word into pieces: five hundred, eighty.
- Write each piece as a number: 500 and 80.
- Add: 500 + 80 = 580.
What is the value of the 4 in 45,120?
- Cut the number into groups of three: 45 and 120.
- The 4 is in the thousands group, in the ten thousands place.
- Do 4 × 10,000 = 40,000.
What is the value of the 6 in 608,734?
- Cut the number into groups of three: 608 and 734.
- The 6 is at the front of the thousands group, in the hundred thousands place.
- Do 6 × 100,000 = 600,000.
Try it yourself
Write this number in digits
seventy thousand and ninety
Write this number in digits
two hundred and twenty-two
Watch out
You put the pieces next to each other: three thousand four hundred and eight becomes 30004008.
Add the pieces instead of putting them next to each other: 3,000 + 400 + 8 = 3,408.
You count the places wrong: for the 4 in 45,120 you write 4,000.
Count the places from the right: ones, tens, hundreds, thousands, ten thousands. The 4 is in the fifth place.
Tips
- Under a hundred you say the tens first: forty-seven is 47, not 74.
- A place that is not in the word gets a 0: three thousand four hundred and eight has no tens.
Why it works
A long number word is made up of pieces you know: thousand, hundred and a number under a hundred. Write each piece as a number and add them, and every digit lands in the right place. A big number like 45,120 is easier to read in groups of three, with a comma between them. Each group has the same three places: ones, tens, hundreds.