Multiplying a decimal by a power of 10 | Decimals | Pre-Algebra | Khan Academy

TL;DR

A step-by-step explanation of how to calculate the cost of buying stamps in bulk.

Transcript

A single postage stamp costs $0.44. How much would a roll of 1,000 stamps cost? And there's really a couple of ways to do it. And I'll do it both ways just to show you they both work. One is kind of a faster way, but I want to make sure you understand why it works. And then we'll verify that it actually gives us the right answer using maybe the mor... Read More

Key Insights

• 🇨🇷 The cost of stamps in bulk can be calculated by multiplying the cost of a single stamp by the desired quantity.
• 👉 Moving the decimal point to the right is equivalent to multiplying by 10.
• 💨 Using the traditional method of multiplying decimals will yield the same result as the faster method.

Questions & Answers

Q: How can I calculate the cost of 100 stamps?

To calculate the cost of 100 stamps, move the decimal point one place to the right, resulting in $44.

Q: What is the faster method to calculate the cost of 1,000 stamps?

The faster method is to start with $0.44 and add a trailing zero. Then, move the decimal point to the right three times, resulting in $440.

Q: Can you explain the traditional way of multiplying decimals to calculate the cost of 1,000 stamps?

The traditional method involves multiplying $0.44 by 1,000. Multiply each digit individually, starting from the right, and place the decimal point correctly. The result is also $440.

Q: How many stamps can I purchase with $20?

Since 1 stamp costs $0.44, divide $20 by $0.44 to find the number of stamps you can purchase. The result is approximately 45 stamps.

Summary & Key Takeaways

• The cost of a single stamp is $0.44.

• To calculate the cost of 10 stamps, move the decimal point to the right one place.

• The cost of 1,000 stamps is $440, obtained by moving the decimal point two places to the right.