If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

### Course: 6th grade foundations (Eureka Math/EngageNY)>Unit 2

Lesson 2: Topic B: Foundations

# Multiplying decimals: place value

Sal uses an understanding of place value to multiply 2.91x3.2. Created by Sal Khan.

## Want to join the conversation?

• At Sal starts talking about the sum being divisible by 1000, but I don't understand why 100 divided by 10 becomes 1000. Can anyone shed any light on this? Thank you
• He says that because 100 x 10 = 1000. get it?
• Please bear with me, just a dumb kid asking a dumb question. Couldn't you just line up the decimals and multiply like normal? And if not, why?
• Unlike adding/subtracting decimals, lining up the decimal points to multiply the numbers provides no value. It usually causes you to have extra work due to the zeros you put in as placeholder.

You are better off ignoring the decimal points while you are mulitplying. Multiply as usual. When you are done, then you determine the placement of the decimal point. This is done by adding the number of decimal digits in each original number. It tells you how many decimal digits your answer needs.
For example: 3.25*1.3
-- Ignore the decimal points. Multiply 325*13 = 4225
-- Determine the number of decimal places: 1st number has 2 decimal digits and 2nd number has 1. 2+1 = 3 decimal digits for the answer.
-- Place the decimal point in your result so that you have 3 decimal places: 4.225

Hope this helps.
• What is comput?
• how was that 7 years ago?
• Never mind. Why is it so hard to remember it all and do it. Make it much more easier if you want people to be able to learn this
• you are cool
(1 vote)
• Aren't you supposed to place the decimal points? When multiplying?
• When multiplying decimals, you can first ignore the decimal points and multiply as usual with whole numbers. In the end, place the decimal point to the left by the total number of decimal places in the two decimals being multiplied. In this way, multiplication of decimals differs fundamentally from addition of decimals (which requires aligning the decimal points first before adding).

Have a blessed, wonderful day!
• Man, this Sal guy is really great! He is the only reason I am passing my super hard math class lol.
• so what I have a really easy math class and this Sam guy teaches decimals which is fifth grade math and Im only 3rd grade so i get early lol xd
(1 vote)
• So with this concept, I could redo 5.06*75 as 506*75, and later take 37,950.0 (the product of 506*75) and move the decimal over 2 numbers (because I moved it 2 numbers to the right to make it a whole number) to get 279.5?
Thank you Sal!!
• do you guys like call of duty warzone
• No! Roblox is the best game not CoD.
• I don't understand the regrouping made by Sal. Why is it 291*32/100/10? For me the logic of rewriting (even though it gives the same result) would be (291*32):(100*10). No?
• Both regrouping methods are correct and get you the correct answer. In fact, they are basically the same method, just Sal chooses to explain it a little bit differently.
• I'm so confused with multiplying decimals. I would LOVE some help! please?
• First just ignore the decimal points and multiply the whole numbers as usual. Then in the end, count the total number of decimal places in the numbers being multiplied, and move the decimal point that many places to the left in your answer.

Example: let's say you're asked to multiply 6.3 * 0.24.
First multiply 63 * 24 to get 1512.
Note that 6.3 has one decimal place, and 0.24 has two decimal places. The total is three decimal places. So move the decimal point three places to the left to get a final answer of 1.512.

Note that multiplying decimals, unlike adding and subtracting decimals, does not require lining up the decimal points first!

Have a blessed, wonderful day!