Multiplication trick for fast calculation | Summary and Q&A

TL;DR

Multiply numbers that are multiples of nine by rounding up to the next ten number, then take off 10%, resulting in the answer.

Key Insights

• #️⃣ The trick for multiplying numbers that are multiples of nine involves rounding up to the next ten number and subtracting 10% of the result.
• #️⃣ It can be applied to any multiple of nine number between 18 and 81.
• ✖️ The trick simplifies multiplication by eliminating the need to multiply by single digits.
• ❓ Practicing percentages is beneficial in mastering this trick.
• 😎 The trick may not be the fastest method but is considered useful and cool.
• 🛝 Rounding both numbers and subtracting 10% twice is also an option for the trick.
• 👻 The trick allows for variations in the choice of numbers to round up.

Transcript

good day welcome to the techmath channel what we're going to be having a look at in this video is it's a cool little trick on how to multiply numbers at are multiples of nine I'll give you an example of these These are numbers like uh uh 9 18 27 81 45 bra da and had a little trick for multiplying with these numbers okay so an example for this is as... Read More

Questions & Answers

Q: How does the trick for multiplying numbers that are multiples of nine work?

The trick involves rounding up one of the numbers to the next ten number, multiplying it with the other number, and then subtracting 10% of the result to obtain the answer. It simplifies the multiplication process for these specific numbers.

Q: Can the trick be applied to any multiple of nine number?

Yes, the trick can be applied to any multiple of nine number, ranging from 18 to 81. It follows the same steps of rounding up to the next ten number and subtracting 10% of the result.

Q: What is the purpose of rounding up to the next ten number?

Rounding up to the next ten number simplifies the multiplication by eliminating the need to multiply by a single digit. It makes the calculation easier and quicker.

Q: Why is it necessary to subtract 10% of the result?

Subtracting 10% of the result ensures that the answer is accurately calculated. It is a step in the trick to account for any rounding errors and adjust the final answer accordingly.

Summary & Key Takeaways

• The video demonstrates a trick to multiply numbers that are multiples of nine.

• The trick involves rounding up one number to the next ten number and multiplying it with the other number.

• After multiplying, 10% of the result is subtracted to obtain the final answer.