The statement a is p percent of b represents the proportion where b is base, a is a part of the base and is the percent.

Let x is the unknown number.

The word y be 10% of a number x represent the proportion .

Simplification of proportion is .

Apply cross products property: If where then .

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Substitute the value of in the proportion .

Multiply each side by .

Cancel common terms.

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The number is 5y.