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Old 01-28-2007, 07:43 AM
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For those days when you forgot your soapstone, calculator, or have a hangover you can add or subtract using your tape measure folded over on to itself ether adding or subtracting too or from your original number. Just remember it won't work for smaller numbers like 2+3 because you might break your tape. :evil:
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Old 01-28-2007, 10:21 AM
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I always use my fingers for smaller numbers...
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Old 01-28-2007, 03:02 PM
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And I always thought that "higher mathematics" was any thing that required me to take my shoes off... RED
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Old 01-28-2007, 04:51 PM
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Here's a little trick that I use and have taught in the apprenticeship math class that I teach, when trying to find half of a fraction. If you know how to do this it takes less time to do it by hand, than it does on the calulator.

Example: 123 11/16"

First: Take the whole number and lower it the the next EVEN whole number. 122"

Second: Divide that whole number in half. 61"

Third: Double the denominator. (16x2= 32)

Forth; Add the numerator and demominator together. (11+16= 27)

Answer: 61-27/32"

123-11/16"
122"
61"
61- ?/32"
61-27/32"

On even whole numbers, just divide the whole number in half, double the denominator and just move the same numerator down to the doubled denominator.

Example: 122-11/16"

61"
61- ?/32"
61-11/32"

I've used this little trick for quite a few years, in the shop and field and it works faster than trying to do it on the calulator.

In the classroom I'd give the students 8 seconds to figure this out on the calulator and by the time they had got them out of their pockets and turned them on, I'd already have the answer on the board.

Just thought I'd pass this on, since most of us always are working with fractional numbers.
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JD2 Model 3 hydraulic Tubing bender with
quite a few expensive dies

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Last edited by Diverbill45; 01-29-2007 at 01:20 AM.
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Old 01-28-2007, 05:01 PM
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Quote:
Originally Posted by Diverbill45
Here's a little trick that I use and have taught in the apprenticeship math class that I teach, when trying to find half of a fraction. If you know how to do this it takes less time to do it by hand, than it does on the calulator.

Example: 123 11/16"

First: Take the whole number and lower it the the next EVEN whole number. 122"

Second: Divide that whole number in half. 61"

Third: Double the denominator. (16x2= 32)

Forth; Add the numerator and demominator together. (11+16= 27)

Answer: 61-27/32"

123-11/16
122"
61"
61- ?/32
61-27/32"

On even whole numbers, just divide the whole number in half, double the denominator and just move the same numerator down to the doubled denominator.

Example: 122-11/16"

61"
61- ?/31"
61-11/32"

I've used this little trick for quite a few years, in the shop and field and it works faster than trying to do it on the calulator.

In the classroom I'd give the students 8 seconds to figure this out on the calulator and by the time they had got them out of their pockets and turned them on, I'd already have the answer on the board.

Just thought I'd pass this on, since most of us always are working with fractional numbers.
now that is good stuff right there!
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Old 01-29-2007, 02:27 PM
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Bill, is it wrong that after that math class, my head hurts?
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Old 01-29-2007, 03:15 PM
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Take 7-15/16" divided by 1/2.
To get that number, you read 7, then 1/2, then 1/4, then 1/8, then 1/16, and added them together to get 7-15/16.To measure you must disassemble the whole mess and then read 7, then 1/2, then 1/4, then 1/8, then 1/16 and mark it on the stock.

Read the ruler the "other" way R-->L and you have 8 - (minus) 1/16" Right every time.
----

To divide by say half, read the measurement but do not add it together, leave it as parts.
1/2 of 7 = 3-1/2
1/2 of 1/2 = 1/4
1/2 of 1/4 = 1/8
1/2 of 1/8 = 1/16 and
1/2 of 1/6 = 1/32

Read it directly on the ruler (no assembly and disassembly of numbers) and mark the stock.

First time or two you use it, it only seems confusing, but all the adding and disassembling of the numbers is what is usually causing the confusion.

-----------------------

If possible always use the same measuring device to both measure and then to cut. All tape measures are not the same. Some of the cheap ones have markings that vary over their length. To check, fold the tape back upon itself and see if the markings on one portion of the tape match the markings on the second section.
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  #8  
Old 01-29-2007, 03:17 PM
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Naw Dirt, that's okay, don't worry about it. After each one of my math classes my head even hurts and I'm the d**n instructor.

Thank God we've progressed above and beyond the slide rule era. Now wasn't that a fun time, to be had, in math class.
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Retired welder/fitter of UA local #290, Portland, Oregon

Miller Dialarc HF-P
Miller 251 wire feed/ with Alum. spool gun purchased from Wyoming (Roy)
Thermal Dynamics 52 Plasma
7" x 12" Horiz. Bandsaw
Weld Craft TIG Torches
JD2 Model 3 hydraulic Tubing bender with
quite a few expensive dies

One Big Ass Mistake America

Always remember ...... a government large enough to give you everything you want is also big enough to take everything you have.
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  #9  
Old 01-29-2007, 05:04 PM
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Since I Machine metal more than I butcher wood I work more with decimals. I don't get many requests to get it to 1/16"..

Although I have had some say, with their fingers spread apart, "about this long." I say "hold that while I get my tape measure" just before I ask if they can out run my .45... Patience my ***...
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  #10  
Old 01-29-2007, 05:25 PM
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IforgeIron, .......... I'll have to work with that one.

Basically, the reason I posted the info was that, on occasion, I've been asked to figure out what half of a large fractional number is and didn't have a tape or calculator with me, at the time, so I'd just used this method, and in about 2 to 4 seconds, I'd have the answer.

There is a little 2 part trick involved and here's where it comes into play. Say someone asks you to figure out what half of 157-15/32" is. It doesn't matter if it's a large or small number. As soon as they give you that number, you already have over half the problem worked out, because you know that you need to figure what half of 156 is, which is 78. (Always remember when given an ODD whole number, drop down to the next EVEN whole number.) Then the denominater, which in this case is 32, automatically doubles to 64. (Always double the denominator.) These first 2 steps are the whole trick. Then the only real math that has to be done is adding 15 and 32 together, which is 47. Answer: 78-47/64".

Now, where things will be a little different, is when given an even whole fractional number, say 134-15/32". You'd have to figure out what half of 134 is, which would be 67. ALWAYS double the denominator, in either case. Then in this case, just move the same numerator (15), no adding needed, above 64. Answer: 67-15/64"

Your figure was 7-15/16". As soon as I read that I already knew that I was going to divide 6 not 7 in half, which is 3, 16 doubles to 32 and 15+16 is 31, answer: 3-31/32".

I've used other methods, in the past, and when someone showed me this years ago, it just seemed to be the fastest way, for me, without having to have a calculator or a tape measure around, and believe me I'm no whiz when it comes to math.

Good info, I always like to get new ideas and tricks from others, thanks for the tip.
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Retired welder/fitter of UA local #290, Portland, Oregon

Miller Dialarc HF-P
Miller 251 wire feed/ with Alum. spool gun purchased from Wyoming (Roy)
Thermal Dynamics 52 Plasma
7" x 12" Horiz. Bandsaw
Weld Craft TIG Torches
JD2 Model 3 hydraulic Tubing bender with
quite a few expensive dies

One Big Ass Mistake America

Always remember ...... a government large enough to give you everything you want is also big enough to take everything you have.
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