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If the sum of digits of a number add to a multiple of 9, then the original number must be a multiple of 9.

You can multiply by nine on you fingers if the number is less than 10. Just hold up all your fingers (and thumbs) and put down the finger the represents the number you are multiplying. Lets say we want to multiply 7 by 9. Just put down finger 7. You will have 6 fingers to the left of finger 7 and 3 on the right, giving you 63. Or use 9. Put down finger 9, and you have 8 to the left and 1 to the right. Yes, 9 times 9 is 81.

The rule given at the top is why the finger trick works. You have 10 fingers, and if you put one down, you have nine. When multiplying any number between 1-10 by nine, adding the the digits of the product always gives nine - the same number as there are fingers left.

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Q: What is a way to multiply the 9 easily?
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What are multiples of 9 and 24?

Just multiply the two numbers to get it (which is, by the way,231)


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3 multiply 9 = 27


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9 oz is how many spoonfuls?

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To convert F to C, subtract 32, then multiply by 5/9 77-32 = 45 45x5/9 = 25 Going the other way, to convert C to F Multiply by 9/5, then add 32


What is the multiple of Number 9?

There are an infinite number of multiples of 9! A multiple is what you get when you multiply something. The multiples of 9 are: 9, 18, 27, 36, 45, 54, 45, 63, 72, 81, 90, and so on, going up by 9 each time (forever). (1, 3, and 9 are FACTORS of 9, by the way - numbers that multiply to give 9)


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One way is to multiply 3 and 7 in order to get 21 and then add 9 to 21 in order to get 30.


How do you turn Celsius into Fahrenheit?

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What two numbers multiply to get 9 and add to get 14?

23