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### Course: Staging content lifeboat>Unit 14

Lesson 52: Multiplying and dividing with powers of 10

# Multiplying a decimal by a power of 10

Learn to multiply 0.44 times 1000 using powers of 10. Created by Sal Khan and Monterey Institute for Technology and Education.

## Want to join the conversation?

• At how do you get 4.40\$?
• Each single stamp costs \$0.44. The stamps come in rolls of 1000.

So, you have 1000 stamps, each costing \$0.44 each.

If you only wanted 10, multiply 10 x \$0.44 to get \$4.40 for 10 stamps.

If you want 100, multiply 100 x \$0.44 to get \$44.00 for 100 stamps.

If you want 1000, multiple 1000 x \$0.44 to get \$440.00 for 1000 stamps.

Notice, the decimal is "moving" to the RIGHT each time? That's what makes the "multiplication by 10's" so easy! You just move the decimal to the right, one place for every 10 that you're multiplying by.

10 is just 10 (also known as 10^1)
100 is 10 x 10 (also known as 10^2)
1000 is 10 x 10 x 10 (also known as 10^3)

This comes in handy when you're using the metric system.
• if you just have 1000x5 how many places do yuo move your decimal point
• Because you can always add as many zeros as you want past the decimal dot, 1000 x 5 is equivalent to 1000 x 5.000 .

Then, you simply move the dot three times to the right, because 1000 is ten to the power of three.
5.000 → 50.00 → 500.0 → 5000

The result is 5000. I hope that helped.
• Where do you put the decimals?
• You put the decimal depending on the problem. If you know the anwser to the (e.g) two numbers multiplyed then you would count the amount of number behind the decimal point in the multiplication and in your anwser you would put the decimal point before the number that you added.
For Example:
32.8 x 4 the answer to this without the demical point is 1312 then you look at how many numbers are behind the decimal point in the problem, which would be 1. Then you count on your anwser (starting to your right going left) that amount and you put your decimal point there. Answer : 131.2
• do we only move the decimal as many times given?
• as many zeros you multiplying by. ie .55 times 10,000 equals 5,500 the decimal move four times because there four zeros after the 1.
• what if ther is 3000000000000000times10 you gone move that all 0s
• You just add one more 0 to it
so 3000000000000000 times 10 = 3000000000000000 plus one more 0 is equal to 30000000000000000. Sal just shows why we do it.
• explain why is 10/100 less than 8/10
• If you simplify 10/100, you will get 1/10. 1/10 is surely less then 8/10.
• What is the value of 0.6× 0.35
• 6*35=210. move decimal 3 to the left since you have 3 to the right spaces =.21
• please give me an every day example of when you would use power
of ten in real life