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# Multiplying decimals and whole numbers with visuals

Multiplying whole numbers and decimals can be fun. It starts with simple examples, such as multiplying 3/10 by 4, and then moves on to more complex examples, such as multiplying 52/100 by 3. In each case, we demonstrate how to use a number line or model to visualize the process and find the product. Created by Sal Khan.

## Want to join the conversation?

• i don't get it or any math for that matter but i'm trying as hard as i pssibly can
• and also couldn't you just do a fraction problem?
ok so say we have 52 hundredths right? we put a 1 under the 3 as 3 over 1 to make it a fraction.
then we do 52/100 *3/1
the answer is 156 over 100 or 156/100.
then divide. 156 divided by 100 is 1.56! 52*3 is 156!
so couldn't you just do a a fraction problem to make it easier?
I just do those to make it easy :D
• Good thinking. Yes, that is possible. Yet we are basically doing the same thing as decimal multiplication with the same number of steps as fraction multiplication. Actually, there are fewer steps as you have to convert it to a fraction (Though this step is very quick and easy to do in your head.) Both ways are perfectly fine and will always give you the same answer with no significant difference in difficulty or speed.
• i love number lines!!

they make math easier to understand, especially when first learning something.
• I hate number lines they are so annoying i have to use them in math class for no reason
• can't you just do 3x4 and then just move the decimal to the left in your answer and the same with 3x0.2 just do 3x2 and move the decimal to the left in your answer and it would make it easier or would be harder or the same.
• how would this apply to like say, 0.05 X 70?
(1 vote)
• Hi,
Well, like shown in the video:
0.05 x 70:
5 x 70 = 350
Then, add up the number of place values after the decimal point, which is in this case 2.
3.50
You can ignore all the zeroes after a nonzero digit (after the decimal point, that is).
0.05 x 70 = 3.5
• how do i do dividing demials . Do you do that
• Hi million 4577! To divide decimals, you have to set it up just like regular division. Once you have that set up, you have to make sure both the divisor and dividend are both whole numbers. To get the dividend to a whole number, you have to move the decimal point up. So, however many places to the left it was in your dividend, you will have it that many places left in your answer. Then, you just have to divided normally. If you had 12.3 divided by 3, you would move up the decimal point and then divide to get 4.1. It would be 41 if this was normal division, but since we moved the decimal point up, it's 4.1. Hope this helps. Have a great day! 😄
• thanks this is very usefull for me because i used to struggle with this but now i just fly right through this
(1 vote)
• what would be a fast way?
(1 vote)
• number lines don't make sense to me.