Basic Math & Pre-Algebra For Dummies
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You can tell whether a number is divisible by 2, 5, 10, 100, or 1,000 simply by looking at how the number ends — no calculations required.

Divisible by 2

Every even number — that is, every number that ends in 2, 4, 6, 8, or 0 — is divisible by 2. For example, the following bold numbers are divisible by 2:

Every even number is divisible by 2 (two).

Divisible by 5

Every number that ends in either 5 or 0 is divisible by 5. The following bold numbers are divisible by 5:

Every number that ends in either 5(five) or 0(zero) is divisible by 5(five).

Divisible by 10, 100, or 1,000

Every number that ends in 0 is divisible by 10. The following bold numbers are divisible by 10:

Every number that ends in 0(zero) is divisible by 10 (ten).

Every number that ends in 00 is divisible by 100:

Every number that ends in 00 is divisible by 100 (hundred).

And every number that ends in 000 is divisible by 1,000:

every number that ends in 000 is divisible by 1,000 (thousand)

In general, every number that ends with a string of 0s is divisible by the number you get when you write 1 followed by that many 0s. For example,

900,000 is divisible by 100,000.
235,000,000 is divisible by 1,000,000.
820,000,000,000 is divisible by 10,000,000,000.

When numbers start to get this large, mathematicians usually switch over to scientific notation to write them more efficiently.

About This Article

This article is from the book:

About the book author:

Mark Zegarelli is a professional writer with degrees in both English and Math from Rutgers University. He has earned his living for many years writing vast quantities of logic puzzles, a hefty chunk of software documentation, and the occasional book or film review. Along the way, he’s also paid a few bills doing housecleaning, decorative painting, and (for ten hours) retail sales. He likes writing best, though.

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