Pre-Calculus All-in-One For Dummies
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When you write a long number, you use commas to separate periods. Periods are simply groups of three numbers. They help make long numbers more readable. For example, here’s about as long a number as you’ll ever see:


The following list breaks this number down into periods.

Quintillions 234
Quadrillions 845
Trillions 021
Billions 349
Millions 230
Thousands 467
Ones 304

This list helps you read the number. Begin all the way to the left and read, “Two hundred thirty-four quintillion, eight hundred forty-five quadrillion, twenty-one trillion, three hundred forty-nine billion, two hundred thirty million, four hundred sixty-seven thousand, three hundred four.”

When you read and write whole numbers, don’t say the word and. In math, the word and means you have a decimal point. That’s why when you write a check, you save the word and for the number of cents, which is expressed as a decimal or fraction.

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