# Ask Tom: How to Find Measurements Without Math

• posted on March 1, 2016, 6:54 pm

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• posted on March 1, 2016, 8:32 pm
On 3/1/2016 11:54 AM, Seymore4Head wrote:

(sigh) Disappointing. He can't divide by 2? "evenly"
(Um, Tommy, every number can be divided -- by any other number -- "evenly"; it's just that the result may not be a nice convenient number for you to deal with!)
I just drilled a 2-7/8 hole offset 7-3/4 by 3-1/2 from a corner ("reference").
Center of 2-7/8 is:
one half of 2 -- let's call that 1!) once half of 7/8 -- let's call that 7/(8*2) = 7/16
Offset by 3-1/2 is 4.5+7/16 Offset by 7-3/4 is 8.75+7/16
You mean to tell me you can't find the "8.75" mark on a scale and count (on your fingers) seven more of the 1/16th markings??
I'm more interested in *real* tricks: e.g., find the center of a given circle!
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• posted on March 1, 2016, 9:49 pm
On 3/1/2016 2:32 PM, Don Y wrote:

Or even more interesting is to find the square root of -4. Any takers?
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• posted on March 1, 2016, 10:06 pm

Type in search:
square root -4.
Finding the center of a circle is just as easy.
--
Dan Espen

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• posted on March 2, 2016, 1:56 am
On 3/1/2016 4:06 PM, Dan Espen wrote:

real number that is the square root of -4.
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• posted on March 2, 2016, 5:41 pm
On 03/01/2016 04:06 PM, Dan Espen wrote:
[snip]

And the other one?
One thing I remember from college is that EVERY number has TWO square roots. The other one is -2i. I even understand that.
Consider that when you find square roots, you halve the angle. For 4 (0 degrees = positive) roots are 2 (0 deg, 0+0=0) and -2 (180 deg, 180+180=0). For -4 ( 180 deg = negative) , roots are i2 (90 deg, 90+900) and -i2 (270 deg, 270+2700).
Another thing, every number has 3 cube roots. However, that is more "complex". It took me about 30 years to understand that (including how that must be true). In case you care, polar representation makes more sense here, where the cube roots of 8 are 2 (0*3=0), 2@120 (120*3=0), and 2@240 (240*3=0).
Now, you can find the fourth roots of 16. Yes, there are 4 of them.
--
Mark Lloyd
http://notstupid.us/
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• posted on March 2, 2016, 5:59 pm
On 3/2/2016 10:41 AM, Mark Lloyd wrote:

Some of us (depends on your age and type of primary school education) learned how to "do square roots" by hand (sort of like "long division").
Do you realize that a similar process exists for "doing" cube roots?

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• posted on March 3, 2016, 6:46 pm
On 03/02/2016 11:59 AM, Don Y wrote:
[snip]

I had a class in college where we would find square roots by hand.
[snip]
--
Mark Lloyd
http://notstupid.us/
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• posted on March 1, 2016, 10:23 pm

What kind of trees have Square Roots ? ? ?
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• posted on March 2, 2016, 3:46 am
On 3/1/2016 5:23 PM, snipped-for-privacy@unlisted.moo wrote:

The ones sawed down by lumber jacks with board feet?
--
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Christopher A. Young
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• posted on March 2, 2016, 5:43 pm
On 03/01/2016 02:32 PM, Don Y wrote:
[snip]

--
Mark Lloyd
http://notstupid.us/
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• posted on March 2, 2016, 5:57 pm
Hi Mark,
On 3/2/2016 10:43 AM, Mark Lloyd wrote:

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