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### Course: MAP Recommended Practice>Unit 34

Lesson 40: Multiplying and dividing whole numbers by 10, 100, and 1000

# Multiplying and dividing by 10, 100, 1000

Learn how multiplying and dividing whole numbers by 10, 100, and 1,000 shifts the digits of the number left or right, respectively. Multiplying increases the place value, while dividing decreases it, making the process easier to understand.

## Want to join the conversation?

• why is math so hard they should make it easy plus who made math anyway?
• Archimedes made math. He was the father of mathematics
• When dividing 3 by .6 is this the method that I can use?

(3 x 10 ) divided by (.6 x 10)
30/6 simplified 15/2
And that’s how you do it or did I miss a step or didn’t do something correctly I need to under stand better the concept of this method
• Yes it's actually a method that I personally use to eliminate the decimal place but here you accidentally simplified 30 / 6 to 15 / 2. It should be 15 / 3 = 5.
• can you please explain it better
• this is so easy like legit just add however many zeros to your number for multiplication and subtract some zeros for division it's that easy!
(1 vote)
• where does the placeholder zero go
• The placeholder 0 goes whenever you move on from multiplying the one to multiplying the ten of the bottom number. For example: 23 x 45. You first do the 5 x 3 and the 5 x 20, then those are what make the first answer which you add to the second number for the complete answer. For the second one, you add the placeholder before doing 40 x 3 and 40 x 20. Then you add the products of each and you get the complete product.
(1 vote)
• In one of the examples Sal showed us, he showed 75,000 divided by 100. If you cross out the zeroes in 100 (or any other 1 with zeroes) and the same number in 75,000, don't you get the same answer?
• Since in the problem 75,000 divided by 100 one hundred has two zeroes and the answer has two zeroes less, wouldn't it be easier to cross off two zeroes from both numbers and then divide?
• what are some `equations for multiplying i need to warm up. at `, ` 4:35, and `, nothing works.
• If the "450" was "451", then when it is divided by 10 the "1" at the end of 451 will be in the decimal tenths(45.1).
• Yes, that is correct. Dividing a number by 10 shifts the decimal point one positive to the left.
• Hi, I didn't understand the last sum. Is the ans 1980.00? (1980)
• I'm assuming your talking about the question where 198,000 was divided by 1000.

No the answer is 198. Because there are three zeros in 1000, you'll shift all the digits three places to the right. This follows the same pattern that you saw with the examples prior. When you multiply by 1000, because there are three zeros, you shift all the digits three places to the left. Now because your dividing by 1000, you'll shift all the digits three places to the right.

So the 1 in 198,000 becomes a hundred (hundred thousand -> ten thousand -> thousand -> hundred).
The 9 in 198,000 becomes a ten (ten thousand -> thousand -> hundred -> ten).
The 8 in 198,000 becomes a one (thousand -> hundred -> ten -> one)

I hope that makes sense.