ive been a ironworker for the past 5 years..recently joined a carpentry shop..natural woodwooker by blood both my father & grandfather were carpenters...i JUST LEARNED THIS TRICK 2 WEEKS AGO from my Supervisor Mickey Nardone
When I worked in the lumber yard,we had a high-school Deca student girl,that was in danger of flanking out of math class because she didn't understand fractions; I got her a tape measure & we went to the warehouse where the dimensional lumber and plywood was kept; for several days my boss allowed me to help her with " lumber yard" fractions- basically the exact same method you used in the video! On the day of her math test,she came to work with a smile on her face & a copy of the test with an A- minus on it! She said the teacher told them they couldn't use calculators or cell phones in his class...but he didn't mention anything about a tape measure;( the math teacher knew she was a D.E.C.A. student & worked that class at our lumber yard & didn't think anything out of the ordinary when she came to class with her company issued tape measure) she told me later ,when she had a hard set of fractions to add or subtract,she pulled her tape measure out a couple of inches & figured out the answer! I wish more teachers & young people could learn " lumber yard fractions" Back in 1965 when I was in the 1st grade,we learned " math" on wooden ruler with a metal straight edge. Just before our D.E.C.A. student graduated from high-school, we had one of our regular yard hands call in sick & we had a large order for some custom cut lumber...our student volunteered to go out in the yard & help get the order cut to specifications! It made me proud when the order went out on time & no mistakes made in the custom cut lumber! Sometimes the old ways are still the best way!
Glad it worked for her. Now if that was a common core school she would have gotten an F even if the answer was right. Good thing the teacher wasn't an A-hole
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@@DennisMathias If you know how to use a slide rule you can do the type of addition shown in this video faster in your head than fiddling with a tape measure.
I've never seen anyone else doing this until now. My dad taught me that trick when I was like 5 or 6. When he was teaching me how to read a tape measure (way before we were taught fractions in school). He wasn't a carpenter but a union construction laborer so he worked around carpenters. Dad growing up during the depression started working early and made sure us kids did too. I was 6 the summer between 1st and 2nd grade when he was putting 1xs on a roof on an addition to our house when he first had me cutting boards for sheathing with a circular saw. I'm sure he would have get in trouble for that now days but I've been sawing ever since and still have all my fingers so ....
Great video. I will say I stopped using imperial measurements 2 decades ago after getting out of school. The metric system is so much quicker and more accurate when doing simple math.
Old carpenters know lots of neat tricks, especially with folding rules and angle squares. As an Instrument Fitter, I was taught to write everything down in base 16 so 5 7/16" is written as 5.7. If I needed greater resolution for say 1/4"OD tubing and below, I would add a 32nd by putting a + sign behind so 5 15/32" is 5.7+. The whole process that we were taught of simplifying fractions just wastes time. Of course, just going metric is also a nice idea if you can but wasn't practical when using materials sized to imperial dimension.
As a Pipefitter, I have used the same trick for years taking out for fittings and marking pipe length. I also learned to fold the tape and connect the 2 measurements then read the tape at the end for adding and subtracting. Measure up to add and down to subtract.
Here's another trick to add to your tool bag: Easy way to divide odd fractional measurement in half (find midpoint): Say you want to find half of 17 3/8" Reduce the 17 to the next lower whole inch and divide by 2 (16/2 = 8) Add the top and bottom of the fraction (3+8 = 11) Put that sum over the next smaller fraction (11/16) Midpoint of 17 3/8" = 8 11/16" Do it a few times on paper, and it will become very easy to do it in your head.
You really should stress that this only works if the number of whole inches is odd, and that it gives the wrong answer if you try it with an even number of whole inches. I know you wrote it was for odd numbers, but I think it could be easaily overlooked. Pretty nifty trick though.
Clarification: In the above method, "odd" is not a synonym for "unusual." It is +mathematical+ odd. The method fails if the whole number is an EVEN number. Example: Half of 6 3/4 is not 3 7/8. It'll always work when the whole number is ODD: Half of 7 3/4 is 3 7/8.
@@cybermanne Dividing *even* measurements with fractions is easy. Why would anyone need a "trick" to divide an even measurement? I very clearly started the comment with "Easy way to divide _odd_ fractional measurement in half"
@@mikerew9132 I also acknowledged that you stated it was a method to divide odd numbers. The reason to use the same trick with even numbers is possibly that it might be percieved as easier to not have to even worry about doing different methods depending on odd or even. I just thought the method could to with an extra "warning label".
Thanks for sharing, I’ll remember this one. I must admit, I use the metric system in calculating, measuring and weight, but always had trouble with fractions. Thanks to you and Bob for helping me out on this one👍
nice. i actually have used this trick before in a different way. it's a lot quicker/easier hanging the 2nd number off the edge like that. ;) i would just make a mark for the first number, measure out the 2nd number from that mark and that is where i needed to cut or give me the total measurement.
As a wood pattern maker I would do that a lot just to figure out how long a piece I needed to cut to extend an already cut piece. Mostly when cutting staves. I also would add or subtract fractions in my head. Taught many apprentices how do subtract a larger fraction from a smaller. Such as 3 7/16 minus 1 7/8. Pattern making involved a lot of math for sure. Nice to see someone else doing this.
My dad was a commercial glass glazier. One of the smartest, and best, men I ever knew. He was born into a very poor Central Texas family in 1923. He never set foot in a school room as a student and was functionally illiterate his whole life. But he had more than his share of common sense and he knew numbers inside and out. He could add, subtract, multiple, divide and work out angles with his trusty 25’ metal tape. I never really got the hang of what was going on in his head. Amazing. He passed was in in 2004 at the age of 81. I wish I had spent more time learning from him!
Its so much easier to use metric. When I first started working I was given the task of adding up all the dimensions on the plan of a large slab sided office block that was in a long string of imperial measurements of feet, inches and various dissimilar fractions, as the guys on site had set out the two sides and they were different lengths. I spent all day doing the arithmetic and couldn't get them to match or even get consistently close, eventually I got a close consensus and passed it on to someone else to resolve. Had it been dimensioned in metric it would have taken me 5 minutes with a calculator or ten minutes by hand.
@Magpie I grew up with imperial, feet inches, ergs and dynes etc but we changed 50 years ago and honestly, having used both extensively there is no doubt that the metric system is infinitely easier and much, much quicker. As a country we still use miles, furlongs and chains and most people I know can easily converse in both methods. Indeed, I have had intelligent detailed professional discussions using a combination of both systems simultaneously.
@@nilpo yes I'm sure you could say 32 ⅔mm but just why would you? Can't measure it with a Vernier or micrometer, nobody recognises it other than being a bit odd and it contradicts the whole straightforward, easy to get your head around concept of the metric system.
@@nilpo yes and no. Sure, you *can* use fractions in the metric system, but typically, you do not. If you need more precision than millimetres, you use micrometres, but you've then entered the realm of engineering, not carpentry. Similarly, you can go from micrometres to nanometres. And yes, there are further, higher precision scales* if you really need them, but then you're well beyond engineering and in the world of particle physics. * They're really not separate scales, the prefixes represent specific powers of ten: pico (10^-12), femto (10^-15), atto (10^-18), zepto (10^-21 ), yocto(10^-24). For example, the diameter of a Hydrogen atom is believed to be around 212 picometres (2.12*10^-14 metres) in diameter. What fraction of an inch is that?
@@mattlivingston2192 Oh, I understand how it works. For scientific measurements, sure, metric is fine for defining precision. But measuring in everyday life is more often qualitative, not quantitative. I know they two halves fit in a single inch. If something is 3/8 inches, I know without any thought that I can fit at least three 1/8 inch objects in that space. I wouldn't use inches to measure the diameter of a hydrogen atom to exacting standards. Take cooking though. If recipe calls for 2/3 cups of flour. It becomes almost thoughtless to half the recipe. And that recipe doesn't require the exactness of micrograms. It's also easier to use smaller measurements collectively. If my recipe instead called for 3/4 cups flour, but I only had a 1/4 cup measure. I know without any effort that I need to use my measure cup exactly three times. These applications, while possible, are far less intuitive in the metric system.
Been taking my son to work and teaching him the trade. He's pretty young and struggles with math being a dyslexic. This should work really well for him! Thanks for the reminder of this old trick.
I'm old enough to remember learning to use a slide rule, works exactly the same way but uses log scales to multiply and divide by adding or subtracting a linear distance.
It just scares me to think that we have to always have a trick or hack in order to learn to do simple math in your head. I'm in my 40s and I just don't get that people can't do simple things anymore, but I guess it's something to get used to. I would use this is a second check but it is a great thing to teach when one can't use their head
When I was a young apprentice, my old school Journeyman made me memorize decimal fractions. From that point on it was just adding or subtracting, non of that numerator, denominator stuff. Measurements were dead nuts on every time.
@@TRPGpilot not an option after 70 years of using fractions. It's an entirely different mind-set, like all of a sudden you are going to like liver and onions after a lifetime of avoidance. Not happening...
@@vashon100 Oh yeah, I saw many things along the way, and see many things today, too. Result? Glad I'm retired wouldn't want to be in the business today. Still have a hand tool woodshop to chisel, saw and hammer when I need something real. Also have all ten phlanges and they still work. ;-)
I remember watching my father, one day using his folding carpenters rule and working the sliding metal piece back and forth, like you would use a slide rule, all the while talking to himself in his head. Now my father had been a carpenter since he was a kid during the depression, and had no formal education. He could barely write his name, yet it was obvious to me that he was working some kind of math using that ruler. I never asked him about what he was doing, fearing that it would embarrass him, he was sort of sensitive to his lack of education but I'd be willing to bet he was working something similar to what you've described here. I wish now I'd asked him to explain it to me. He went to Glory many years ago. When I see him again in heaven, I'll ask him about it.
Although i have no problem doing the calculations in my head, I am going to use this method because it is quick and easy, and there are time when i just don't feel like playing human calculator. I like this trick a lot and can't believe I have never seen it before.
Great! Someone that knows what I do. And to answer that guy talking about being all smarty smart using your math knowledge: If you are not smart in this type of math, you don't belong in a business where this is used. If you can't do the math, you are in the wrong business!
when i first started doing vynal sideing work the guy that tought me could lay out metal for bending brick mold to wrap windows the metal is 2 foot wide he would bend it to look like brick mold. it was 3/8 x 1 x 1 x 1/2 x1/2 x 3/4 cut he could go all the way across the 2 foot calling out the numbers for me to mark on the outher side any way it amazed me how he could keep up with all those marks and number like rain man lol
I'm one who was born with the math gene. I did both of them in my head in less time than it would take to pick up the piece of what ever to use the tape measure on, much less the time it takes to do the trick.
The difficulty here is not metric vs. imperial, it's fractions vs. decimal. However, the imperial inch is not a great carpentry unit when using decimals, because 0.1" is too crude and 0.01" is too fine. On the other hand, 1 mm is plenty fine enough unless you are doing really intricate woodwork, yet it's not so fine that it's difficult to line up a pencil mark. For that reason, I find metric easier for carpentry. In the case of machining, imperial measurements are always expressed in decimal inches, so you don't run into this problem.
@@zoso1123 There's nothing wrong with 32nds. It's a little less than 1 mm and a good increment for woodworking. However, unless you express all measurements in 32nds (i.e., 16/32 rather than 1/2), you are back to the problem with fractions. If you've been working with fractions for years, it's no big deal, but it's a system that's prone to mistakes for beginners.
You are using your tape measure as a number line so subtraction can also be done. Put a mark at the minuend and then put your subtrahend on the mark and measure back to the beginning of the board and put a second mark at the 0 on your tape measure. Measure from the end of the board to your second mark and you will have your answer.
@@ronaldclobes9340 How do you know that terminology? I've never heard of those words. Had to look it up. Learned something new. I put it in the video. Thanks. 👍
@@herrickkimball I saw DumbAss Loser's comment on whether this could be used for subtraction so I was initially answering that comment. I vaguely knew the word subtrahend but I wanted to make sure I was using it correctly so I looked it up in the dictionary (Google) and read a few of the questions below the links. Turns out what I thought was the Subtrahend was actually the Minuend and so I had to use both words in my comment so they would stick. I learned a new word today (minuend). Words are fun to use and learning is fun too.
As an old woodworker for almost 50 years, this is never a problem for me! In the thumbnail image for this video, the sum of the equation is 17-13/16. Too simple to solve. I could do it when I was 8 years old!
Millimeters are too small for most measurements and also hard to see for older eyes. The equivalent to the millimeter is 1/16 inch, which is too precise for most jobs.
I'm math dyslexic, and numbers flip themselves in my mind without my even knowing it, so I was horrible with it all through school, still am. I wanted to be a meteorologist, but with all the numbers required, that particular career was out. Most technical careers are, but I'm retired now, so it doesn't matter. Nonetheless, this is a very useful thing for me to know even as just an ordinary retired (woman) of 70.
I do understand what you are doing , but your last scenario could confuse someone or have them make a wrong cut . If I were showing someone how to do that scenario I would have put the end of my measuring tape on the 12 7/16 mark and measure out the addition of the 5 3/8 to come up with the total . Your way showed the correct measurement , but not for cutting the piece shown . I do understand your process though and thank you for the time and effort that went into making this video .
As a draftsman [ old fashioned retired ] I was trained to add numbers and fractions by mental exercise first , slide rule second and calculators third. For everyday use ...this is an incredibly intelligent way of summing two whole numbers and their fractions and it can also be used to subtract going the in the opposite direction .
@@steveoxler9774 Haha. Mate, I grew up with the imperial system, had to convert steel drawings from imp to metric when the Metric system was introduced in Australia. I have no problem working it out, try adding or subtracting fractions on a calculator. Can't understand why you Yanks keep persisting with such a shit system.
@@maxbarko8717 If the metric system had a good equivalent to a foot, I think it would’ve caught on more. We measure so many things in feet, sq. feet, etc, it’s very ingrained. It’s even simple to approximate just by walking it off. The lack of a real equivalent (some fraction of a meter) doomed the metric system here in the US.
@@redstateforever Also, the millimeter is too small and the centimeter too big for most precise measurements. Metric is easier to convert or manipulate the numbers, but that's about it.
Nice. I had the answer in my head within a few seconds. I'm old, so I learned fractions of inches in my younger days. These days everything is metric where I am, so that's what I use now. I like maths tricks. I'm going to show this one to my son.
I think you should teach your son how to do proper maths instead; especially given that inch fractions are so simple as they're based on multiples of 2...
I do something similar. I measure and make a mark at the first number. Then I put the 10” mark on the tape measure on that first pencil mark and then measure the second distance and make another pencil mark. Then hook the tape and pull to the second mark for the total.
Ha ha. Thank you. I just commented on another of your vids that I was going to watch this one. Honestly, I had it in my head before you were finished (because I DO have the math gene, or whatever - OK, I'm old and I was taught to do this and was already on common denominators before the words left you mouth), but it is still a beautiful tip and a gem for when the CD is hard to find.
Cool tip, but the example is pretty easy. 3/8 == 6/16, therefore the fractions add right up to 13/16 with simple addition (7/16 + 6/16 = 13/16). Then it is just 12 + 5 + 13/16 = 17 13/16. Done. No measuring, no tape measures needed.
The best fastest and most accurate method of measure whether calculating rafters ,stairs ,volume ,is using 1 unit of measure .no fractions to make mistakes with .
You could mark your lumber at 12 7/16", then place your 10" graduation of your tape on the mark and count off 15 3/8" which is 5 3/8" and you got your final cut length.
There is a model used in school today to help kids visualize the sum of two numbers. It is similar to Herrick’s (Bob’s) trick. Each number is represented by a rectangle. Both are together end to end and the total is labeled at the top. Now we just need to introduce tape measures in the classroom.
Great trick, I've used it before. From what I hear a slide rule works on the same principle but for multiplication. Any good tricks to share for math with a framing square? I just found an entire (old) book about that subject and was blown away.
There are some great shortcuts using a framing square. Figuring number of risers for a stair and figuring the riser height for each riser. Great stuff like that
Just a tip: take a look at your framing square and pay close attention to the markings on both sides. One side is most likely normal measurements while the other is split up into tenths for some diabolical reason. Don't get them mixed up or you'll screw up whatever you're working on. Especially annoying when trying to do something like cut stair stringers.
We didn't have time to put marks on a board so we just folded the tape over to line up the number and fraction. You can add, subtract and divide on a tape measure.
Haha that's funny you should use the term old-time Carpenter. When I first started out some fifty years ago as a carpenter's helper, I used to refer to all the old guys as old-time Carpenters. Guess I'm one now. Thanks for the tip...
Best way to add/subtract fractions is to commit to learning them in decimal form, and then to never use fractions again. Still, great trick though! Thank you for sharing.
No one showed this on RU-vid because there are easier ways. You don't need the pencil or the piece of wood. You can do this with just the tape measure alone. Fold the tape measure back on itself. Line up the two measurements together with each other. The end of the tape measure shows the sum of the two numbers.
