Multiplying 10s | Math | 4th grade | Khan Academy

TL;DR

By breaking down numbers into their factors of 10, multiplication can be simplified and made easier.

Transcript

• [Voiceover] Let's multiply 40 times 70. So 40 times, we have the number 70. So we could actually list that out, the number 70, 40 different times and add it up. But that's clearly a lot of computations to do. And there's gotta be a faster way. So another way is to stick with multiplication, but see if we can break these numbers up, this 40 and th... Read More

Key Insights

• 🍳 Breaking down numbers into factors of 10 simplifies multiplication and makes it faster.
• 🪈 The order of numbers in multiplication does not affect the answer.
• ❤️‍🩹 Adding zeroes to the end of a number is a pattern when multiplying by 10.
• 🧑‍🏭 Breaking down numbers into factors of 10 is a useful strategy for mental math.
• ✖️ This method can be applied to any multiplication problem.
• ✖️ Understanding the properties of multiplication, such as commutativity, helps in simplifying calculations.
• 🧑‍🎓 Breaking down numbers into factors of 10 is a helpful technique for students learning multiplication.

Questions & Answers

Q: What is the purpose of breaking down numbers into factors of 10 in multiplication?

Breaking down numbers into factors of 10 makes it easier to multiply because the patterns for multiplying by 10 are known, and adding zeroes to the end of numbers simplifies calculations.

Q: Does changing the order of numbers in multiplication change the answer?

No, the order of numbers in multiplication does not affect the final answer. This is because multiplication is commutative, and the order of multiplication does not change the product.

Q: How can we multiply numbers using factors of 10?

We can break down numbers into their factors of 10, such as writing 40 as 4 times 10 and 70 as 7 times 10. Then we multiply the other factors (4 and 7) separately and add the necessary zeroes based on the number of factors of 10.

Q: Can this method be applied to any multiplication problem?

Yes, this method can be applied to any multiplication problem. Breaking down numbers into factors of 10 makes multiplication easier, regardless of the numbers involved.

Summary & Key Takeaways

• Breaking down numbers into factors of 10 makes multiplication simpler and faster.

• The order of the numbers in multiplication does not affect the final answer.

• Multiplying by 10 adds a zero to the end of the number.