Content

• Steps
• Method 1 of 3: Simple addition
• Method 2 of 3: Doubling in Order
• Method 3 of 3: Doubling by Decomposition
• Tips

Doubling large numbers may seem like a daunting task at first, but you just need to practice to see how easy it is. There are various ways of doubling. Study each one, and then use the easiest one for you whenever you have to solve such a problem.

Steps

Method 1 of 3: Simple addition

1. 1 Write an example. In this way, you need to write the example in the same way as any addition example. Just write down the number twice (in a column above each other) and put the plus sign.
   • Example: Double the number 357.
     • Write the example like any addition example: 357 + 357
2. 2 Add the numbers in the right column. Add the rightmost digits (ones). Basically, you are simply multiplying the number of ones by two.
   • Example: IN 357 + 357 on the right is 7.
     • 7 + 7 = 14
3. 3 Move the ten to the left. If the sum of the units is greater than or equal to 10, the ten should be transferred to the next (counting from right to left column) to the other tens. Therefore, in response, for now, write down only units of the resulting number.
   • Example: In our example 14 more 10, so 1 (number ten in 14) should be written above the next column. 4 will answer; this will be the rightmost digit in the final result.
4. 4 Add up the next column of numbers. Add the numbers in the next, counting from right to left, column (tens). If in the previous step you transferred "1" there, this unit also needs to be added to the other two digits.
   • Example: IN 357 + 357 next is the number 5.
     • Since in the past action you moved 1 in tens, you must add it too.
     • 5 + 5 + 1 = 11
5. 5 Repeat to the end of the line. Continue adding the numbers in the same way, column by column from right to left, until you reach the left-most digit of your number.
   • Example: As 11 more than 10you need to transfer 1 into the next category (column), that is, to hundreds. Right 1 will be the next digit of your score (tens).
     • In our example, the last column (hundreds) is left. You need to add the numbers in it, adding the transferred unit: 3 + 3 + 1 = 7
     • 7 will be the left-most digit of the final result.
6. 6 Write down your answer. If you have not already done so, write down the sums of each category one by one. The result will be equal to the original number multiplied by two.
   • Example: The number on the left (hundreds) - 7... The number in the middle (tens) - 1... The number on the right (units) - 4... Recorded together they give 714.
     • So 357 when doubled gives 714.

Method 2 of 3: Doubling in Order

1. 1 Double the left digit. Take the first digit of your number (the leftmost digit, the largest digit). Mentally multiply it by two and write down the result. This will be the first digit or two digits of the answer for the example.
   • Example: Double the number 872.
     • First on the left is the number 8.
     • 8multiplied by two gives 16.
2. 2 Look at the second digit. If the next digit (counting from left to right) is greater than or equal to 5, then 1 must be added to the number obtained in the previous step.
   • If the second digit is less than 5, then nothing needs to be added to the previous result.
   • Multiplying any number between 5 and 9 by two will give a two-digit result, so this step is necessary. Multiplying by two numbers from 0 to 4 will give a single digit.
   • Example: The second digit of 872 is 7... As 7 more 5, to the previous category must be added 1.
     • 16 + 1 = 17
     • This means that the answer will start with 17.
3. 3 Double the second digit. Go back to the second digit and multiply it by two. The result will be the next digit of the final result.
   • If multiplying by two gives you a two-digit result, discard the tens and write down only the ones.
   • Example: Second digit in 872 - This 7.
     • When doubling 7 gives 14.
     • Drop tens (1) and write down only ones (4).
     • Number 4 will stand in the middle of the final answer.
4. 4 Repeat for the next numbers. Do the same for all remaining digits, moving from left to right, until you double the last digit (s) of your number.
   • Example: There is only one digit left in the example.
     • Last among 872 worth a figure 2... So ka 2 less 5, nothing needs to be added to the previous bit.
     • When doubling 2 gives 4... This will be the last digit of your score.
5. 5 Write down your answer. Write down all the numbers obtained one by one. This will be the end result.
   • Example: The first part of the answer is 17... The next figure is 4... The last digit is 4... By writing them down in a row, you will receive an answer. 1744.
     • So 872 when doubled gives 1744.

Method 3 of 3: Doubling by Decomposition

1. 1 Divide the number into parts. Divide the number into its constituent parts according to the categories: units, tens, hundreds, and so on. Write it down in expanded form.
   • Example: Double the number 453.
     • When decomposed into digits, we get: 453 = 400 + 50 + 3
2. 2 Double each piece. Take each part (rank) and double it separately.
   • To double the digits of more than ones (that is, tens, hundreds ...), multiply their first digit by two, and then add as many zeros to the result as there are in the multiplied number.
   • Example: You need to double the numbers 400, 50 and 3 separately.
     • 4 when doubling gives 8, means, 400 gives 800.
     • 5 when doubling gives 10, means, 50 gives 100.
     • 3 when doubling gives 6.
3. 3 Add all the pieces. Sum all the doubling results to write the answer in standard form.
   • Example: 800 + 100 + 6 = 906
4. 4 Write down your answer. The result obtained by adding the doubled values ​​of all parts will equal the doubled original number, and this will be the final answer.
   • Example: 453 when doubled gives 906.

Tips

• The result of doubling any number must be divisible by two. In other words, the answer will always be an even number.