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### Course: Staging content lifeboat>Unit 14

Lesson 52: Multiplying and dividing with powers of 10

# Dividing a decimal by a power of 10: pattern

Discover a pattern when dividing by powers of 10. Created by Sal Khan.

## Want to join the conversation?

• When would you ever have to divide decimals in real life?
• Let's say you had \$61.56 and wanted to buy a bunch of candy bars that cost \$1.62 apiece. How many could you afford?
• I'm a little bit confused. So, say you had the equation: 0.9* 10 would be 09. or 9.0?
(1 vote)
• I like to think of decimals as money. So 0.9 is 90 cents. What's 90 cents * 10? (or, \$0.9 * 10)...well, it can't be 0.09, because that would be 9 cents...why would 10 times 90 cents be 9 cents (which is less than it originally was)? So, 0.9 * 10 must be greater than 90 cents...9.0 or \$9.00!

That's an easy way to remember which way you need to move the decimal in these kinds of problems.
• Why do we have to call a decimal a decimal instead of point?
• decimal means something specific. It means a sign in a number that shows the number has parts of a whole number. The word "point", however, means something different in math and geometry. It is a location, a spot on a graph. a way to remember is, a decimal is divided by ten (deci="ten") and a point is a place you can go to.
• What does arbitrary mean?
• based on random choice or personal whim, rather than any reason or system.
"his mealtimes were entirely arbitrary"
synonyms: capricious, whimsical, random, chance, unpredictable; More
(of power or a ruling body) unrestrained and autocratic in the use of authority.
"arbitrary rule by King and bishops has been made impossible"
synonyms: autocratic, dictatorial, autarchic, undemocratic, despotic, tyrannical, authoritarian, high-handed; More
MATHEMATICS
(of a constant or other quantity) of unspecified value.

All of that is the meaning of arbitrary.
• If you mean by 100. Yes, and the answer would be 0.0986.
• So when you divide by 10, the decimal moves to the left and makes the number smaller? And when you're multiplying by 10, it goes to the right?
• Yes, that is correct. 10.0 divide by 10 gives you 1.00, and 10.0 multiplied by 10 gives you 100.