5 Quick Tricks for Multiplying 2-Digit Numbers Easily

Mathematics can sometimes seem daunting, especially when you're staring down a page of numbers waiting to be multiplied. While calculators have made our lives much easier, it's still beneficial to know quick mathematical tricks to boost your calculation speed. Here's a guide to multiply 2-digit numbers quickly, focusing on mental agility and efficiency.

Trick 1: The Nearest Ten Method

• Choose the nearest multiple of 10 to one of the numbers you want to multiply.
• Subtract the number you’ve chosen from the other number to get the compensation.
• Multiply the number by your chosen multiple of 10 and then add the compensation.

For example, if you want to multiply 23 by 17:

👉 Note: Choose 20 as it's the nearest multiple of 10 to 23.

1. Subtract 20 from 17, which gives you 3 as the compensation.
2. Multiply 20 by 17 to get 340.
3. Add the compensation: 340 + (3 x 17) = 340 + 51 = 391.

Trick 2: The Cross-Sum Method

This method works well when you have numbers close to each other. Here's how it goes:

• Add the two numbers and then multiply them by half their sum.
• To multiply, for example, 22 and 23:

1. Add 22 + 23 = 45.
2. Half of 45 is 22.5.
3. Multiply 22 by 22.5 = 495.

Trick 3: The 11 Trick

This trick is applicable when multiplying numbers by 11:

• Take the number you're multiplying by 11.
• Write down the first digit.
• Add the first and second digits together for the middle digit.
• Write down the second digit.

For example, 24 x 11:

1. Write down 2 (the first digit).
2. Add 2+4 = 6 for the middle digit.
3. Write down 4 (the second digit).
4. So, 24 x 11 = 264.

Trick 4: The Fingers Method

This trick uses your fingers for an easily visualizable multiplication method for numbers from 6 to 10:

• Hold up both hands with your fingers spread apart, palms facing you.
• Assign the numbers from 6 to 10 to each finger starting from the left thumb (6) to the right pinky (10).
• To multiply, touch the fingers of the two numbers you're multiplying.
• Count the fingers to the left of the touched fingers (including the touched fingers) for the tens digit.
• Multiply the fingers to the right for the ones digit.

Let's try multiplying 8 by 7:

1. Touch your left thumb (6) and your right index finger (7).
2. To the left, you have 4 fingers (including touched), making the tens digit 4.
3. To the right, you have 2 fingers (8 – 6), multiply 2 by 2 (7 – 6) to get 4 for the ones digit.
4. So, 8 x 7 = 56.

Trick 5: The Compensating Method

Here's a handy method when you have one number that's not far from a round number:

• Take the number closer to a round number and subtract the excess from the other number.
• Multiply the new, round number with the adjusted second number, then add the product of the excess.

Take 19 x 26 as an example:

1. 19 is close to 20, so use 20 and subtract 1 from 26 to get 25.
2. Multiply 20 by 25 = 500.
3. Add the excess: 500 + (19 x 1) = 500 + 19 = 519.

👉 Note: These methods aren't the exact mathematical operations but can quickly get you close to the result, allowing for minor adjustments if needed.

Mastering these tricks can greatly speed up your multiplication skills, especially when mental arithmetic is preferred or when you want to impress others with your mathematical prowess. The key to proficiency is practice, as familiarity with these methods will make them almost automatic in your calculations. Now, let's wrap up our journey through quick multiplication tricks with a few key takeaways:

• Understanding and applying these methods can save you time and mental effort.
• Practice is crucial; the more you use these tricks, the faster and more accurate you'll become.
• Remember, while these techniques are shortcuts, they might not yield exact results every time; they are meant to be close approximations.

Can these tricks be used for all 2-digit number multiplications?

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These tricks are most effective when the numbers have specific patterns or relationships like being close to 10 or multiples of 11. For general multiplication, traditional methods or a calculator might be more reliable.

Are these multiplication tricks accurate?

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Yes, for the examples given, these tricks yield accurate results. However, they are approximations in some cases and might require minor adjustments.

How long does it take to become proficient in these tricks?

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Proficiency depends on practice. Regularly practicing these techniques can significantly improve your speed and accuracy within a few weeks.