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