Reading and Writing Whole Numbers
Reading and writing whole numbers correctly involves grouping digits into periods of three, using commas after trillion, billion, million, and thousand, hyphenating two-digit numbers between 21 and 99 (like forty-seven), and never using the word 'and' when saying or writing whole numbers — 'and' signals a decimal point. This Grade 7 math skill from Saxon Math, Course 2 is essential for communication in math, science, economics, and any context where large whole numbers appear in written or spoken form.
Key Concepts
Property Put commas after the words trillion , billion , million , and thousand . Hyphenate numbers between 20 and 100 that do not end in zero (e.g., fifty two). We never include "and" when saying or writing whole numbers.
Examples $3,406,521$ is written as Three million, four hundred six thousand, five hundred twenty one. $1,380,000,050,200$ is written as One trillion, three hundred eighty billion, fifty thousand, two hundred. Twenty trillion, five hundred ten million is written with placeholders as $20,000,510,000,000$.
Explanation Writing big numbers is like reading a map where commas are your landmarks, telling you to announce 'million' or 'billion.' Just read the three digit chunk before each comma and say the period name. Remember to hyphenate numbers like seventy six, and most importantly, never, ever say the word 'and'—it's forbidden in whole number land!
Common Questions
How do I read a large whole number?
Separate the digits into groups of three from the right. Each group is read with its period name (ones, thousands, millions, billions). For 3,050,200: 'three million, fifty thousand, two hundred.'
Why do we put commas in large numbers?
Commas separate numbers into groups of three digits (periods), making large numbers easier to read. Without commas, 1000000 is harder to identify than 1,000,000 at a glance.
Which numbers in English are hyphenated?
Two-digit numbers between 21 and 99 that do not end in zero are hyphenated: twenty-one, forty-seven, ninety-nine. Multiples of ten are not hyphenated: forty, seventy.
Why do we not use 'and' when writing whole numbers?
In math, 'and' represents the decimal point. 'Two hundred and five' should be written 205, not 200.5. Saying 'two hundred and five' is ambiguous in mathematical contexts.
When do students learn to read and write whole numbers correctly?
This is introduced in elementary school and reviewed in Grade 7. Saxon Math, Course 2 covers it in Chapter 8 for work with large numbers.
How do I write a large number in words from digits?
Read each group of three from left to right with its period name. For 4,312,075: 'four million, three hundred twelve thousand, seventy-five.'
What are common mistakes when reading large whole numbers?
Students sometimes say 'and' between the thousands and hundreds groups (like 'two thousand and four hundred' instead of 'two thousand four hundred'), or mislabel period groups (billions vs trillions).