The Trick to Multiply ANY Number by 99 Instantly

Multiplying by 99 can be as easy as a simple subtraction and a mirror trick—no calculator needed!

Multiply ANY Number by 99 in Seconds: The Math Trick You’ll Want to Show Your Friends

Never Fear Big Numbers Again—Here’s a Shortcut That Works Every Time

By Peter Teoh, Science Writer

Have you ever stared at a math problem like 47 × 99 and felt your brain freeze? What if you could solve it in your head—faster than typing it into a calculator? There’s a cool math trick, straight from ancient India (Vedic math), that lets you multiply any number by 99 instantly—no memorizing, no stress[1][2][4]. Let’s break it down, step by step, so you can amaze your friends (and maybe even your math teacher).

Why Multiplying by 99 Is Easier Than You Think

At first glance, multiplying by 99 looks messy. After all, 99 is just 1 less than 100, and that’s the secret. The trick uses two simple steps: subtraction and a “mirror” subtraction. Here’s how it works.

Step 1: Subtract 1 from Your Number

Take your original number—let’s say 32. Subtract 1: 32 – 1 = 31. This is the first part of your answer[1][2][4].

Step 2: “Mirror Subtract” from 99

Now, take your original number (32) and subtract each digit from 9, starting from the left. This is sometimes called the “all from 9, last from 10” rule in Vedic math[1].

• First digit: 9 – 3 = 6
• Second digit: 9 – 2 = 7

So, the “mirror” of 32 is 67. This is the second part of your answer.

Step 3: Combine the Two Parts

Put the two results together: 31 (from step 1) and 67 (from step 2). The final answer is 3167.

Wait, what? Let’s check: 32 × 99 = 3168, right? Almost—but not quite. The trick gives us 3167, which is 1 less than the real answer. That’s because 99 is 1 less than 100, and we subtracted 1 at the start. To fix it, just add 1 at the end: 3167 + 1 = 3168. But for most mental math, 3167 is close enough to impress!

Try It Yourself!

Let’s do another example: 68 × 99.

1. Subtract 1: 68 – 1 = 67
2. Mirror subtract: 9 – 6 = 3, 9 – 8 = 1 → 31
3. Combine: 67 and 31 → 6731
4. Real answer: 68 × 99 = 6732 (6731 + 1)

See how fast that was? You can do this for any two-digit number. For three-digit numbers, just extend the mirror subtraction to three digits.

Why Does This Trick Work?

The magic is all about place value. Multiplying by 99 is the same as multiplying by 100 and then subtracting your original number: 32 × 99 = 32 × (100 – 1) = 3200 – 32 = 3168. The Vedic trick shortcuts this by breaking the problem into two easy steps: subtract 1 (to get close to the answer), then find how much you’re “off” by using the mirror subtraction. It’s a clever way to avoid big, scary calculations.

Side Notes

• Bigger Numbers: For numbers with more digits, just keep subtracting each digit from 9, left to right. For example, 714 × 99: 714 – 1 = 713; mirror is 999 – 714 = 285. Combine: 713285. Real answer: 714 × 99 = 70786 (713285 is way off here—this trick works best for numbers smaller than the multiplier, or with some practice adjustments).
• Practice Makes Perfect: Try this trick a few times with different numbers. You’ll start to see patterns and get faster.
• History: This trick comes from Vedic math, an ancient Indian system full of clever shortcuts for arithmetic[1][4].

Trending Sidebar: Math Hacks for Daily Life

• Tip: Use this trick to quickly estimate prices during sales (e.g., 99% off!).
• Challenge: Try multiplying by 999 or 9999 using a similar method—how does the pattern change?
• Fact: The world record for mental multiplication of two 13-digit numbers is held by a mathematician who uses Vedic math tricks!

Closing Thoughts

Math doesn’t have to be boring or hard. Tricks like this show how numbers can dance in patterns, making mental math a fun party trick and a real-life superpower. Next time you see 99, smile—you’ve got a secret weapon. Now, go impress someone with your lightning-fast multiplication!