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Multiplying by 7 x 11 x 13: A Nifty Trick
Ever find yourself needing to multiply by 7 x 11 x 13, but you don't have a calculator handy? Don't worry, there's a clever trick that can help you do it quickly in your head! This method relies on a visual pattern, making it easy to remember and apply.
The Trick:
Let's say you want to multiply 23 by 7 x 11 x 13. Here's how the trick works:
- Write down the number you want to multiply (in our case, 23).
- Double the first digit (2 x 2 = 4) and add the second digit (4 + 3 = 7).
- Write down the second digit (3) next to the number you just calculated (73).
- Now, multiply the original number (23) by 1001 (since 7 x 11 x 13 = 1001). This is simple: just add three zeros to the right of 23, giving you 23000.
- Finally, subtract the original number (23) from the result (23000 - 23 = 22977).
That's it! You've successfully multiplied 23 by 7 x 11 x 13 using this trick.
Why Does This Work?
The trick works because of the special relationship between the numbers 7, 11, and 13. When you multiply them together, you get 1001. The steps we follow are essentially breaking down the multiplication into simpler operations.
Let's visualize this:
23 x 7 x 11 x 13 = 23 x 1001
By multiplying by 1001, we're essentially adding three zeros to the right of the number. The steps involving doubling and adding digits ensure that we're subtracting the original number to get the correct answer.
Practice Makes Perfect
This trick might seem a little confusing at first, but with a bit of practice, you'll be able to multiply by 7 x 11 x 13 in no time! Try it out with different numbers and see how quickly you can get the answers.
This trick is not only useful for quick calculations but also a fun way to impress your friends and family with your mental math skills. So, next time you're stuck without a calculator, remember this handy trick!