Sunday, December 6, 2009

OCTAL MULTIPLICATION

We multiply the numbers as they are. However, 2 digit or 3 digit products will still remain in one column. As you can see, when we multiplied 5 by 6, we write a 30 below. Not 0 carry 3. Do the following for 2 times 6 to get 12 and so on.

Next, we add the numbers. 30 + 0 is 30. 12 + 5 is 17. 0 + 2 is 2. Sums are still on individual columns.


Here's the tricky part. Since we're dealing with the octal number system ( 8 ), we have to find multiples of 8 closest to each digit. These are 0, 8, 16, 24, 32, 40, 48 and so on...For 30, the closest would be 3 x 8 = 24. So subtract 30 by 24 to get 6. Carry the 3 over to the second digit.

The number we carry over is determined by the number of 8's we had to subtract from 30 to get a difference of less than 8. I.E 30 - 8 = 22 - 8 = 14 - 8 = 6. We subtracted 30 by 8 three times so we add 3 to the digit before. Or it is simply the number we multiply by 8 to get the number closest to 30.

17 + 3 is 20. The multiple ( of 8 ) closest to 20 is 16. So we subtract 20 by 16 to get 4 and carry over a 2 to the 3rd digit.

2 + 2 is 4 . Since this is less than 8, this would be the final answer.

3 comments:

  1. Thank you for the article it is simple and helpful. Well explained too. This is my address www.martinnjoroge.webs.com

    ReplyDelete
  2. Thanks for writing in simple and explained way

    ReplyDelete
  3. This comment has been removed by the author.

    ReplyDelete