Last modified on 24 November 2008, at 21:43

Long addition

Long addition is a simple, fairly long winded, but highly useful method of adding multi-digit numbers together.

Imagine that we are adding 205 to 876.

  • Firstly, write the numbers above each other. Make sure that the digits of both numbers are clearly aligned according to their place values (i.e. hundreds, tens and units). Leaving a definite space between your columns helps avoid confusion, especially with larger sums.
  • Then, it is as simple as adding the columns. Begin in the units column and work from right to left.
  • In our example, adding 5 and 6 gives 11. 11 can be thought of as 1 ten and 1 unit. The unit is recorded in the answer box in the units column. The ten must be "carried" into the tens column, so the next operation is 7 + 0 + 1 = 8. The eight is recorded in the answer box in the tens column.[1]
  • Finally, we add the digits in the hundreds column (8 + 2 = 10).[2] The zero is recorded in the answer box in the hundreds column, and the one is placed in the answer box in a new thousands column.

Picture8ol0.png

Footnotes

  1. Properly speaking, this operation is 70 + 0 + 10 = 80.
  2. Similarly, 800 + 200 = 1000.