jankyrre

Dont laugh,but how do you guys calculate lenght an easy way.
Ex. Finding the total lenght of 2'3 5/8"+8 15/16"+10 29/32"=

Is there a trick to it ,or do you have to put up a calculation with
fractions and common multiplies.

Professur

simply convert all to /32 and add.

FMB42

Convert fractions to decimals and have at it.

oldcutlass

I convert to decimals so: Ex. Finding the total lenght of 2'3 5/8"+8 15/16"+10 29/32"= 24 + (3.625 + 8.9375 + 10.90625) /12 = 3.9604166 feet which converted back = aprrox 3' 61/64

allyolds68

There is no easy way. Here in America we are Metrically Challenged. They should have put us all on the short bus when we were kids, taken us to Europe, and beaten some sense into us. We have no idea how easy the rest of the world has it.

joe_padavano

Math with fractions has NOTHING to do with SAE or metric units. This is grade school math. Professur has it exactly correct. The only part of this that requires knowledge of "english" units is the part that 2 ft = 24 in.

2'3 5/8"+8 15/16"+10 29/32"

2 ft = 24 in, 5/8 = 20/32 so 2 ft 3 5/8 in = 24+3+20/32, or 27 20/32 in

15/16 = 30/32, so 8 15/15 = 8 30/32 in


Now add all the whole numbers: 27+8+10 = 45 in.
Add all the fractions: 20/32 + 30/32 + 29/32 = 79/32 = 64/32 + 15/32 = 2 15/32

The total is 45 + 2 15/32 = 47 15/32 in (or, 3 ft, 11 15/32 in).

You were going great until the feet to inches thing at the end, proving once again that this is a fractions problem, not an SAE/metric problem.

allyolds68

A base 10 system is logical. A base 32....errrrr, 12......errrrr.....whatever ..... Is not. Comparatively speaking there is no "easy" way

oldcutlass

Oops brain fart. 3' 11.468 inches

joe_padavano

While I understand what you are trying to say, the fractions above are still in a base 10 system. It's not like we're talking binary or hexadecimal. And to really blow your mind, you can just as easily write fractions using base 2, 12, or 16. Personally, we had fractions drummed into our heads in grade school back in the 1960s, long before calculators were even invented. Doesn't speak well of the educational system today.

Of course, we also had to walk five miles to school.

In the snow.

Uphill.

BOTH WAYS!

garys 68&72

2'3 5/8"+8 15/16"+10 29/32
2'3 1/2 + 9 + 11 = 3' 11 1/2.... close enough. Ever framed a wall? Your answer would be 48"
Use the right tool for the job, ie. a micrometer in 0.001" if you need more accurate

allyolds68

I had the worst of all worlds. In the early eighties when I got out of college and started as an Engineer the bridge plans were all generally in decimal feet, but all the carpenters that worked for me worked in feet and inches. I knew off the top of my head (to two decimal places) all the eighths..ie 1' -5 3/8" = 1.45' . In the mid to late eighties the federal government decided that all bridge drawings had to be metric. That became more challenging to convert for the carpenters so I started buying folding stick rulers with metric on one side and feet and inches on the other. Locate the dimension on one side of the ruler, flip it over to get the conversion. I even taught the foreman to do it. Then a few years later we abandoned the metric system and went back to US Standard Units.....But don't throw away all those rulers because hundreds, if not thousands of bridges had already been designed using metric units. Many of the projects were shelved to be built later. Today I was working on a demolition drawing for a project that bid in 2011 and was metric. All the existing drawings from the original bridge that I need for reference are US Standard. In CAD I just work in "units", so metric is definitely more logical

Professur

This. I learned math using a slide rule. Walked out of exams well ahead of the poor suckers trying to use a calculator. Fractions I do in my head. But then, I also do hex and binary too. Metric is a sad dumbing down for the masses. Laziness and nothing more IMO. You do far more complicated math in your own head just catching a ball.

jaunty75

The trick is called converting everything to a "common denominator." Anyone paying attention learned it in about fourth grade.

http://www.mathsisfun.com/numbers/co...nominator.html


After you complete this lesson, you're ready to go on to learn how to subtract fractions!

MDchanic

I'll just echo Joe and Jaunty and Koda: This is a fractions problem, and a painfully simple one, at that, since they can all be brought to an easy common denominator.
It's nothing like 3/7 + 8/9 + 2/17, for instance. I mean, they're all roots of 2, for chrissakes.

Do they not teach operations with fractions in Europe?
And what if you had to divide them?!?

I absolutely don't see why this is a problem.

Imagine how hard your computer has to think to do simple decimal operations when it thinks in binary, but communicates in hexadecimal!

- Eric

jankyrre

It is not a problem for me,
I do it the same way as you. But the thing is that it takes me a couple of minutes to add those lenghts,so I was just wondering if you really did it that way.

rustyroger

Remember 12 inches equals one foot and go from there.

For the fractions you need to find the lowest common multiple (aka denominator)
Easy in this case , it's 32.
5/8 = 20/32
15/16 = 30/32
and 29/32 Now add the Numerators (the top figures in the fractions)
= 79/32

Divide 79 by 32 and you get 2 15/32.

2'3" is 27 inches (12 inches = one foot)
Add 8" and 10" and the 2" from the fractional calculation, = 47"
Divide 47 by 12 and you have 3 11/12. Three feet eleven inches.
Add the fraction, you have 3' 11 15/32". Just short of four feet.

To convert to millimetres (UK spelling) multiply inches by 25.4 This isn't perfectly precise, but fine for construction or sheet metal work, accepted as an international standard.

47
25.4
18.8
235.0
9400
=1193.8

One metre 193.8 millimetres. The hard bit is converting 15/32" to millimetres.
You could cheat and simply round it up to 16/32", which is 1/2" = 12.7mm

That gives you 1206.5mm. Well within the tolerances of a GM body assembly plant or a construction site.

If you need exact precision you have to express 15/32 as a decimal, then multiply by 25.4. I left full time education over forty years ago, I can't remember how to do this at short notice. I'll figure it out and let you know .

Roger.

rustyroger

I remember now!.

1/32 = 0.03125. OK, I confess, I used a calculator. I put in 1/32= to get this figure.
So multiply .03125 by 15.
0.03125
15
15625
31250
= 0.46875"

Multiplied by 25.4; 46875
254
187500
2344750
9375000
=11807250
11.8mm to one decimal place. 11.80725mm to be perfectly precise.

Remember where the decimal point should be. It's common sense, if you get it wrong you end up with an answer out to a magnitude of 10, 100 or more. If you work out how long your Oldsmobile is in metric terms and come up with 400 metres, well that's the length of a drag strip!. 4 metres is about 17 feet, I'm sure you can follow the reasoning.

Gonna take an aspirin and lie down for a while........

Roger.

Professur

I'll wager I know why you find it difficult. You probably have trouble keeping multiple lines of thought running simultaneously. No worries, it's hardly taught anymore. Except for musicians. But it's easily learned. Ever wonder how a drummer can have both hands and both feet all working independently, and then add the task of singing on top of that? Practice. That's all it takes. Begin with keeping one set of numbers in your head. Random numbers, a set of 7 3 digit numbers is sufficient to start. Write them down somewhere and take a couple of minutes to memorize them. Don't bother carrying the list with you. Then, during the day, while you're working on something, pick two of them and add them together, without stopping whatever task you're doing. Brewing coffee, climbing a ladder, whatever you do in a day. Fully half the people you meet during the day won't be able to do this simple task while walking around a corner. But with a little practice, you soon will. Then when you've gotten bored of this, add a third task ... singing or humming a tune. Doing math in your head while singing is actually easier than you'd think.

It's all the same as patting yourself on the head while rubbing your tummy. Just a question of training yourself.

joe_padavano

I do frame walls, and in that case I'd use 47 1/2". We have no idea what the OP is doing with these numbers, however.

joe_padavano

NASA still requires metric for satellites with "english" conversions in parenthesis. I've seen a lot of drawings out of places like JPL where a dimension is something like 25.4 (1.00).

Yeah, they're designing in metric units.

Fortunately, the Air Force uses "english" units alone - one of the many reasons why I prefer working for them.

Allan R

Metric is not hard. Neither is SAE. We've had metric in Canada since 1976 so the last 2 generations haven't known anything different than Europeans. Miles vs kilometers, Celsius vs Fahrenheit, mph vs kmhr, quarts vs liters. This whole discussion is being over analyzed. Q asked in p.l 1 and properly answered in p.l 2

Koda

You rrrrrrrang, my friend?

It behooves us to be proficient in both systems. My tool sets are fully redundant in both. However, I have some opinions on the systems, and there actually are advantages to both. Many in the US, being either liberal, modernist, Europhiles, or some combination of the above, love themselves some metric system just because they like the idea of it, and often despise anything US-centric because they hate their native country.

Leaving politics out of it per the forum rules, I like both systems and I'll list some brief things I've noticed.

Temp: Yes, Celsius is based on water phase changes, but Fahrenheit is a more precise unit, and, for most parts of England and the USA, 0 is as cold as it gets, and 100 is as hot as it gets.

Fractional measurements: Metric millimeters are easier to follow, but the increments of the standard system are 1/2 the difference in the increments. To wit, there is no socket half the difference between a 10 and a 15 socket, but there is in the US system's equivalents. Plus, a 1/32 increment is smaller than a mm, although I do have a 3.5 mm socket.

Caliber: I shoot, and I find the decimal of an inch system easier to visualize than the mm diameter. However, the metric case designation is sometimes more useful than a caliber and brand name. But, if you know them both, you can screw with people. 7.62x63 very few people recognize (it's 30-06).

jaunty75

Unlike all the others, this is not a "metric vs non-metric" thing. The Fahrenheit scale was based on the freezing point of a brine solution on one end (0 F) and the approximate human body temperature at the other (about 100 F).

The Celsius scale is based on the freezing and boiling points of water, and so makes those values nice round numbers. But neither scale has anything to do with the factors of 10 that the metric scale uses for length, volume, and so forth.

D. Yaros

The real question is:

If Train A leaves Des Moine, IA at 2300 hrs., heading east, travelling at 37.5 MPH, and
Train B leaves Detroit, MI at 0115 hrs., heading west, travelling at 26.3 MPH

At what time, and where, will they meet?

joe_padavano

Uh... so?

People typically don't make sockets for bolt sizes that don't exist. More to the point, the size of the wrenching feature is not directly connected to the size or load capacity of the fastener.

Koda

So, it's not precise, which was my point. Your second point is very correct, but it's usually the external clearances of the fasteners that cause the problem with the size, not the capacity. It's amazing how automotive hides bolts these days.

jankyrre

Well if you by a metric socket set it usually contains one for every mm.
The standard sizes are:
10 mm socket for 6mm bolts
13 mm. 8mm bolt
15 mm. 10mm bolt
Etc.

12,14,16,18mm sockets are hardly used.

joe_padavano

I find that on newer GM vehicles, it's 10mm then the odd numbers. On Honda, it seems to be more of the even numbers. Possibly by shaving the head size for a given fastener, they save a few grams on each. It adds up.

joe_padavano

If you mean clearance to the head (and the wrench), I agree.

Professur

Um .. since you don't run two trains in opposite directions on the same track .. never.

oldcutlass

Are they electric trains?

jankyrre

More confusing stuff.
1 US gal.is 231 cid.
1 Imp.gal. is 277,4 cid.
Even if the Imp.gal.is larger,1 Imp.fl.oz.is smaller than an US fl.oz.

There is even a unit called Gill.Is that used anymore?

Erinyes

I love this thread beyond all reason.

On the other hand, I teach math.

MDchanic

Actually, they do, and did, since the inception of railroads.

When railroads were invented, there was no such a concept as "lanes" in roads, and travellers would just pull over a bit to let each other pass.
On top of this, believe it or not, it costs twice as much to build two tracks as it does to build one.
Because of this, railroads have (and still do, whenever possible) run on single tracks. This is one of the reasons why railroad schedules have always had to be so precise: a single track could carry two trains coming right toward each other at full speed. It was essential that one reach a switch and a siding at the right time, so that it could be shunted to the side to allow the other to pass safely.
Many terrible railroad accidents occurred over the years because one train was travelling at a different speed than expected, or because a man was "asleep at the switch."

Besides, the answer is 09:20, in South Bend, Indiana.

- Eric

MDchanic

Not that confusing.

The US gallon had been used for centuries as a wine measurement, and was determined by the fact that one gallon weighs eight pounds (ie: each pint weighs a pound, whence the old saying, "A pint is a pound the whole world 'round"), and is divided into four quarts, eight pints, sixteen cups, thirty-two gills, or 128 ounces.

The Imperial gallon was a newer English concession to the newly popular metric system, which had been introduced by the French.
It was defined as the volume of water that weighs ten pounds, and also divided into four quarts, eight pints, sixteen cups, or thirty-two gills, but into 160 ounces instead of 128.
This meant that the Imperial gill was made up of five ounces, while the American gill was made up of four ounces, while the volume of a single ounce was nearly identical in each.

In both systems, the ounce is further divided into eight drams, 24 scruples, and 480 minims, though the exact volume of each varies slightly, as the US minim is equivalent to 0.062ml, while the Imperial minim is equivalent to 0.059ml, a difference of three thousandths of a ml (0.000003 liters).
We don't use these measures much anymore, though I do have a few vessels on the shelf that are graduated in them.

And, speaking of English peculiarities in units, I haven't heard a peep out of Roger about Whitworth tools.
Having done a small bit of work on English motorcycles, I think that Whitworth deserves at least a mention.
If you want your metric brain to bend around something really perverse, pick up a set of Whitworth wrenches and start workin'.

- Eric

Seff

We can argue all day about how calculating fractions of inches is done and whether everybody should be able to do it or not, and I agree that it should be doable. But anyone claiming (and I'm not accusing anyone here) that metric isn't simpler and thus easier to work with, I can't agree with.

garys 68&72

I'll switch to the metric system when they burry me 2 meters underground. ;-)

rustyroger

Ok Eric;

The sizes marked on Whitworth wrenches (I know the correct term is "spanner", but I'm talking to ex colonials here ), refer to the diameter of the threads of the fasteners.
I don't have any tables that give the corresponding across the flats measurements for the various sizes.
BA threads have different rules again.
No doubt there are other obscure anachronistic systems that someone can recall?.

Joseph Whitworth deserves much more recognition than he gets. Essentially he standardised threads and wrench sizes for British industry, so a mechanic from any part of the Empire would know what size wrench he would need, and what size thread he would find on any given fastener.
Europe and America went their own ways, but recognised that a standard system was needed.
The Metric system will eventually emerge as the universal standard, whatever its merits and faults, Imperial and American systems of measurement are used by less (as a percentage) of the developed and developing world as time goes by.

I remember from my schooldays Rods, Poles, Perches, Pecks, Grains, Bushels and Furlongs.
As a child I had to deal with the pre decimal English currency until 1971.

Jankyyre, is there anything else you want to know?.

Roger.

MDchanic

Yeah, I'm kinda sad that I missed farthings, guineas, shillings, and ha'pennies, but at least I got to experience day-to-day life with Lire, SwissFrancs, DeutschMarks, and Francs before the Steamroller of Sameness crushed them all.

- Eric

Octania

the Steamroller of Sameness crushed them all.
=================
interesting terminology

I think folks should be ABLE to add fractions of oddity but it should never be required. Now comes the day when we meet extraterrestrials who dominate us and we find out that they use 1/13 and 1/17 and 1/43 fractions as the basis of all things measured. Yah all prime number denominators too. Make 'em into decimal or other-than-ten base numbers and it gets easier... by far. I don't see why anyone would even bother with fractions or fractional tool sizes. What a PITA to memorize. Especially if your memory is kludgy like mine is. When we need to win the next big war, like WWII, efficiency will matter and fractional stuff just drags you down.


As for being able to add numbers while working and humming a tune.... no.


i cannot even REMEMBER such a lot of numbers all day. Unless they are Olds casting numbers. I cannot remember two 2-digit numbers while I walk across the room. Easily distracted. Skill sets vary. I don't understand music and could not play an instrument if I had to either.

PS site problems?
once again all the above text disappeared when I hit ENTER due to being directed to a login page. This problem has not pestered me in years. Can it be fixed. This time I saved all text before hitting ENTER and did not get hosed.