Multiplication of decimal

Lysbilde: 1
Louise, I'm confused about decimal multiplication. Do you understand it?
No, I still don't know where the decimal goes. I hope Ms. Crezil goes over it again today.
Lysbilde: 2
Good morning. Many students find decimal rules confusing.
Yesterday we learned about decimal multiplication.
I want to make sure you understand how to do it correctly.
Lysbilde: 3
When we add or subtract decimals, we line them up. Do we also do this when we multiply?
Theordie?
Lysbilde: 4
That's right, Juan. We line up the numbers and multiply like normal.
Then we count the digits to the right of the decimals in both factors.
Finally, in the product, we count from right to left the same number of places and put the decimal point there.
Lysbilde: 5
Okay, let's try a practice problem. What is 4.21 x 3.8?
It's 15.998!
Awesome job! Can someone explain why Sheila put the decimal between the 5 and the 9?
Lysbilde: 6
Louise?
I get it now! There are 3 digits to the right of the factors, so we have to move the decimal point 3 places to the left in the product.
You're right! Great explanation!
Lysbilde: 0
No, we have to line up the numbers.

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