Multiply Large Numbers without a Paper or a Calculator

A. Multiply the Big Numbers close to 10, 100, 1000, etc

In this section, we cover the steps to multiply big numbers which are close to numbers like 10, 100, 1000.

Note: The base number to address this problem is 100 that is with two zeros. So the final answer is a combination of two numbers with each one having two digits.

Steps to Multiply Big Numbers

Let us take a simple example before we multiply big numbers. In the below steps we multiple 96 and 97.

Step1: Identify the Base Number

In this case, the base number is 100 as both the numbers are of two-digit numbers.

Step2: Subtract both the numbers from Base Number

  • 100 – 96 => 4 is the first number (N1)
  • 100 – 97 => 3 is the second number (N2)

Step3: Next Derive the sum and multiplication of the  numbers N1 and N2

  • Sum of the two numbers is 7 (4+3)
  • Multiplication of these two numbers is 12 (4X3)

Step4: Next Derive the two parts of the Final answer

  • Part1 – Base Number – Sum => 100 – 7 => 93
  • Part2 – Multiplication that is 12

Note: If part2 is a single digit,  prefix it with zero to make it a two digit number. For example in 99X98, Part2 will be 2, so you need to make it 02),

Step5: Final Answer

Join both the parts to get the final answer, that is 9312

 

How to Multiply Big Numbers with a template

In this example, we are multiplying 997 and 998. In this case, both the numbers are of 3 digit length, hence the base number would be 1000.

Example How to Multiply Big Numbers close 10,100, 1000

 

Download Practice

You can download the following image and print for practice. Practice this problem enough times so that you can do it in your mind without paper.

Practice Template How to Multiply Big Numbers Close to 10 100, 1000

 

B. Multiplay Any Number with 11

This multiplication is very easy. The number of Digits in the results will be one more than the number which you are multiplying with 11.

Multiplay one Digit number with 11

We all know this easiest multiplication by muscle memory. Just repeat the number, for example, 8X11 = 88

Multiplay a two Digit number with 11

In this case, the result will be a three digit number.

Step1: Write down both the numbers leaving one number gap between

Step2: Add both the numbers and write down in the middle gap. In case the sum is more than 9, add one to the left number.

Multiply 2 Digit number with 11

Multiply a three Digit Number with 11

This method will apply for any number with any number of digits. Actually, in the above pictures for a two digit number, the same method was used.  The Result will have write 4 digits, so keep four boxes.

Step1:   Write first and last digits in first and last boxes.

Step2: Add each paid of numbers and keep the sum in the middleboxes. In case the sum exceeds 9, Carry 1 to the previous box.

Multiply 3 Digit number with 11

 

Final Words

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