Multiply Numbers Between 11 and 19: A Simple Math Trick

Multiplying Numbers Between 11 and 19: A Simple Math Trick

Are you tired of struggling with multiplication problems, especially when dealing with numbers between 11 and 19? There's a simple and clever trick that can make these calculations a breeze! This method relies on basic multiplication facts and a little bit of addition, making it easy to learn and apply.

The Trick

Here's how it works:

1. Identify the 'tens' digit: Look at the number you're multiplying. The 'tens' digit is the one in the tens place (e.g., in 13, the tens digit is 1).
2. Add the 'units' digits: Add the 'units' digits of the two numbers you're multiplying. (e.g., in 13 x 17, the 'units' digits are 3 and 7, so 3 + 7 = 10).
3. Combine the results:
• If the sum of the 'units' digits is less than 10, simply place it next to the product of the 'tens' digit. (e.g., for 13 x 16, 1 x 1 = 1 and 3 + 6 = 9, so the answer is 19).
• If the sum of the 'units' digits is 10 or more, add 1 to the product of the 'tens' digits, and place the 'units' digit of the sum next to it. (e.g., for 13 x 17, 1 x 1 = 1, and 3 + 7 = 10. Adding 1 to 1 gives 2, and the 'units' digit of 10 is 0, so the answer is 20).

Examples

Let's see some examples to solidify the trick:

• 12 x 15:
• 'Tens' digit product: 1 x 1 = 1
• 'Units' digit sum: 2 + 5 = 7
• Answer: 17
• 14 x 16:
• 'Tens' digit product: 1 x 1 = 1
• 'Units' digit sum: 4 + 6 = 10
• Answer: 24 (1 + 1 = 2, and the 'units' digit of 10 is 0)
• 18 x 19:
• 'Tens' digit product: 1 x 1 = 1
• 'Units' digit sum: 8 + 9 = 17
• Answer: 34 (1 + 1 = 3, and the 'units' digit of 17 is 4)

Why This Works

This trick works because it cleverly combines basic multiplication and addition. When multiplying numbers between 11 and 19, you're essentially multiplying the 'tens' digit by itself and adding the 'units' digits to find the middle digits of the result. The 'units' digit of the sum tells you the final digit of the answer, and if the sum is 10 or greater, you carry over 1 to the 'tens' digit product.

Practice Makes Perfect

Like any mathematical skill, practice is key to mastering this trick. Try it out on different numbers within the range of 11 to 19. You'll be surprised how quickly you can calculate these multiplications! This trick is also a fun and engaging way to learn multiplication facts and develop number sense.

Conclusion

This simple math trick for multiplying numbers between 11 and 19 is a valuable tool for students and anyone who wants to perform these calculations quickly and efficiently. By understanding the underlying logic and practicing regularly, you can confidently apply this method and impress your friends with your mental math abilities!