How to Multiply by 9's in Your Head
Learn the formula., Multiply x{\displaystyle x} by 10., Subtract x{\displaystyle x} from 10x{\displaystyle 10x}.
Step-by-Step Guide
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Step 1: Learn the formula.
The formula is 9x=10x−x{\displaystyle 9x=10x-x}.
This method works for 9 times any number.
In this instance, identify the factor you are multiplying by 9 as x{\displaystyle x}. , Multiplying a number by 10 is easy to do in your head.
All you need to do is add a zero to the end of the number.
For example:9(115)=10(115)−115{\displaystyle 9(115)=10(115)-115}9(115)=1150−115{\displaystyle 9(115)=1150-115} , This will give you the product of 9x{\displaystyle 9x}.For example, 9(115)=1150−115=1035{\displaystyle 9(115)=1150-115=1035}. -
Step 2: Multiply x{\displaystyle x} by 10.
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Step 3: Subtract x{\displaystyle x} from 10x{\displaystyle 10x}.
Detailed Guide
The formula is 9x=10x−x{\displaystyle 9x=10x-x}.
This method works for 9 times any number.
In this instance, identify the factor you are multiplying by 9 as x{\displaystyle x}. , Multiplying a number by 10 is easy to do in your head.
All you need to do is add a zero to the end of the number.
For example:9(115)=10(115)−115{\displaystyle 9(115)=10(115)-115}9(115)=1150−115{\displaystyle 9(115)=1150-115} , This will give you the product of 9x{\displaystyle 9x}.For example, 9(115)=1150−115=1035{\displaystyle 9(115)=1150-115=1035}.
About the Author
Peter Stevens
Creates helpful guides on home improvement to inspire and educate readers.
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