Learn How To Multiply Numbers in the 90s Quickly
Multiplying numbers in the 90s can seem daunting, but there's a simple trick that can make it a breeze! This method uses subtraction and a bit of mental math to get you to the answer quickly and efficiently.
The Trick
Here's how it works:
- Subtract both numbers from 100.
- Multiply the two differences.
- Add a zero to the product.
Example
Let's say you want to multiply 93 by 96:
- Subtract 93 from 100: 100 - 93 = 7
- Subtract 96 from 100: 100 - 96 = 4
- Multiply the differences: 7 x 4 = 28
- Add a zero to the product: 280
Therefore, 93 x 96 = 280.
Why Does This Work?
This method works because it utilizes the distributive property of multiplication. When you subtract a number from 100, you are essentially breaking it down into two parts: 100 and the difference. For example, 93 is the same as 100 - 7. When you multiply 93 by 96, you are multiplying (100 - 7) by (100 - 4).
Expanding this out, we get:
(100 - 7) x (100 - 4) = 100 x 100 - 100 x 4 - 7 x 100 + 7 x 4
Simplifying this, we get:
10000 - 400 - 700 + 28 = 8928
Notice that the first two terms (10000 and 400) are the same as the result we obtained using our trick (280) with an extra zero. The remaining terms (-700 and 28) are simply the differences between the original numbers and 100, multiplied by 100.
Practice Makes Perfect
This trick might seem a little confusing at first, but with a little practice, you'll be multiplying numbers in the 90s like a pro! Here are a few more examples to try:
- 92 x 95
- 97 x 98
- 91 x 99
Have fun multiplying!