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:

1. Subtract both numbers from 100.
2. Multiply the two differences.
3. Add a zero to the product.

Example

Let’s say you want to multiply 93 by 96:

1. Subtract 93 from 100: 100 – 93 = 7
2. Subtract 96 from 100: 100 – 96 = 4
3. Multiply the differences: 7 x 4 = 28
4. 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!