Strategies for multiplying multi digit decimals

TL;DR

Learn how to multiply decimals by using different strategies such as converting to tenths and using estimation.

Transcript

• [Instructor] So in this video, we're gonna try to think of ways to compute what 31.2 times 19 is. And there's multiple ways to approach this, but like always, try to pause this video and see if you can work through this on your own. All right, now let's do this together. Now one way to think about this is you could view 31.2 as a certain number o... Read More

Key Insights

• 💨 One way to calculate decimal multiplication is by converting the decimals to a whole number format, multiplying, and then converting back to decimals.
• 😥 Estimation can be a helpful tool to determine the approximate location of the decimal point in the answer.
• 🥇 Understanding the place value system is crucial for decimal multiplication.
• ✖️ The strategy of converting decimals to tenths simplifies the multiplication process.
• 😥 Estimation can guide the placement of the decimal point to ensure a reasonable answer.
• ✅ Estimation can also be used to check the accuracy of the calculated answer.
• ❓ Estimation techniques are valuable for mental math calculations.

Questions & Answers

Q: What are the two strategies demonstrated in the video for computing 31.2 times 19?

The two strategies shown are converting to tenths and using estimation.

Q: How does the strategy of converting to tenths work?

By viewing 31.2 as 312 tenths, you can multiply 312 by 19 to find the answer in tenths and then convert it back to a decimal.

Q: What is the purpose of using estimation in multiplication?

Estimation helps determine the placement of the decimal point by approximating the product of 31.2 and 19 to an easier-to-multiply pair of whole numbers.

Q: Why is it important to test the reasonableness of the answer using estimation?

Testing the reasonableness of the answer helps ensure that the computed product aligns with the estimated value, providing confidence in the accuracy of the calculation.

Summary & Key Takeaways

• The video demonstrates two strategies for computing the product of 31.2 and 19: converting to tenths and using estimation.

• The first strategy involves viewing 31.2 as 312 tenths, multiplying 312 by 19, and converting the answer back to a decimal.

• The second strategy suggests estimating the answer by multiplying whole numbers and determining the appropriate placement of the decimal point.