Expert: John Zalewski - 6/26/2008

Question
Hi, I already can do math in my head, but when it comes to division, it takes a little longer than multiplying.  Right now, I can do division in my head such as, 176/37, within.. 3 minutes or so.  I was wondering if there was any shortcut with division, like there is with multiplying.  In multiplying, you can take each number and multiply it by each other number (then add the 0's and such).  As of now, I am just doing the full division process in my head, which makes it harder.

Answer
Hello, Patrick.

I find that when I try to do division in my head I usually just divide it as is, without looking for shortcuts.

However, I suppose the same steps could be used for division that are used for multiplication. For example, when I multiply 35 and 18 I come up with 630. I accomplish this by first multiplying 35 and 20, getting 700, and then subtracting two thirty-fives, or 70.


If you divide 16 into 84, you could first multiply 16 and 6, giving you 96. Then you realize 96 is 12 greater than 84, so you subtract 12/16 or .75 from 6, giving you 5.25.

Or you could multiply 5 and 16, giving you 80, and then add 4/16 or .25 to that total, giving you 5.25.

Hope this helps.

Regards,
John