Adding or subtracting mixed whole and fractional numbers can be painful. Forget reaching for a calculator or asking Alexa what the sum is. Instead, two rulers are the simple solution.
Before construction calculators and almost instant online services were available, craftspeople have used a clever method to add up mixed numbers. QUICK! What’s the sum of 7-⅝” and 4 3/16”? That’s what we thought. You can figure it out, but the answer is right there, in plain sight, when you reach for two imperial rulers (by the way, the answer is 11-13/16”).
In the episode, DirtFarmer Jay shows how to get the sum of either numbers added together or subtracted from each other by placing two rulers alongside each other. If you are using imperial numbers (inches and fractions), no conversion to decimals is needed (or even desirable!), the numbers are used “as is”.
So, to ADD 9-13/16 to 2-⅝, locate 9-13/16” on your first ruler. Place your second ruler alongside your first point with the zero point aligned with the first measure. Then read the second dimension on the second ruler; 2-⅝”. Then look at what is directly adjacent on the scale of the first ruler - 12-7/16”. That’s your answer.
A couple of other things as well. First, you can add more numbers by summing the first two and using that as your starting number for the next dimension you’ll add. As long as you have a ruler long enough to accommodate the total, you’re good.
Second, you can also SUBTRACT one number from another by locating the number you want to subtract from on one ruler. Place the zero point of your second ruler across from that measurement. Now measure back down the distance you want to subtract and your answer will be right there on the adjacent rule. Our ancestors were clever, weren’t they?
Lastly, this works for metric measures as well. Although the metric system is based on units of 10, you still get mixed measures between centimeters and millimeters or adding units such as 4.5 cm and 22 mm. Two metric rules will solve the problem speedily.
By the way, we love using the Woodsmith Fine Tools etched rulers. If you’d like to purchase your own, you can visit http://bit.ly/DFJWoodsmithRulers. We don’t receive a commission or compensation of any kind should you decide to add these precision tools to your toolset - we just like telling others about what works really well in our shop.
There you have it - another great technique you can use from now on. Even “gnarly” numbers can be summed without anything besides a couple of rulers - and you can JUST DO IT YOURSELF.
Hey, Dirt Farmer Jay here from DirtFarmerJay.com.
If you're a maker like I am,
you're gonna add a lot of mixed numbers together
to make pieces of material,
whatever material you're working with.
Now, you sure, if you've got Alexa in your shop
or Makerspace, you can call out and say,
hey, how much is nine and 13 sixteenths
plus two and five eighths?
Or you can get out your calculator
or construction calculator and do that.
But why, when you've got what you already need
right before you, a pair of rulers.
Stay tuned and I'll show you a great trick
you'll use over and over again.
Hey, Dirt Farmer Jay here from DirtFarmerJay.com.
I love great simple tricks that many people
over the generations before us have used.
And this is one of those tricks of using a pair of rulers
to add mixed numbers.
Now, mixed number is where you have a whole number,
plus you have a fraction with it.
And a lot of times those fractions
end up with differing denominators.
One of them may be in a 32nd,
the other may be in a 16th or a quarter
or an eighth or whatever it may be.
And when you try to add those things together
really quickly and efficiently,
you can introduce a lot of error
or it's just can be real difficult.
So look on down here.
Here's a couple of fraction type of things.
We're gonna let the ruler solve for us.
We're gonna add seven and five eighths
plus four and three sixteenths and see what we get.
And we're also gonna do nine and 13 sixteenths
plus two and five eighths.
This also works the opposite way
where I can actually subtract and you'll see what I mean,
but let's just do the addition right now.
So what I'm gonna do is I'm gonna first lay down one ruler
and I'm using these Woodsmith fine tools.
I love these rulers by the way,
and I'll give you a link below where you can get them.
But as you can see from your vantage point,
you can see the same numbers that I do.
So you're seeing a four and I'm seeing a four on this side.
So let's go ahead and do our first number.
And that's seven and five eighths.
So if I move right up here to seven and five eighths,
it's right there.
And I'm gonna add four and three sixteenths.
So the only thing I'm gonna do is take my second ruler.
I'm gonna butt it up to my first
and I'm gonna go to that seven and five eighths right there.
And then I'm gonna use, I'm gonna jump to ruler two.
This is ruler one.
We're gonna go to ruler two
and I'm gonna use my four and three sixteenths.
So I'm gonna go four plus three sixteenths
and there go back to ruler A
and there is my answer right there.
I am at 11 and I go to three quarters,
but that's not right.
It's actually 13 sixteenths.
So 11 and 13 sixteenths.
So we'll do 11 and 13 sixteenths.
Not bad for writing upside down, right?
And the rulers did that.
Let's try it again just so we make sure
this really works well.
So we're gonna do that again.
We're gonna go here.
We've got our numbers we're gonna add right here.
Nine and 13 sixteenths plus two and five eighths.
Go to our first ruler, ruler A.
Nine and 13 sixteenths is right there.
And then we're gonna butt the ruler right there
at nine and 13 sixteenths.
And we're gonna go ahead and add two and five eighths.
And I need to move that over a little bit
cause I'm not being as accurate as I could.
There we go.
I'm gonna go two and five eighths right there.
And there's my answer right there.
It is 12 and seven sixteenths.
So we're gonna put that down and do 12 and seven sixteenths.
Now you can do the opposite as well.
If I was subtracting out nine or two and five eighths
from nine and 13 sixteenths, I could do the same thing.
I could just go, let's go nine and 13 sixteenths
and put two and five eighths on that nine and 13 sixteenths
right there and go backwards.
And then I get my answer over here.
It's pretty spiffy, isn't it?
Well, these great historical tips really serve us well
in the modern maker shop.
If you have a tip like this that you'd like to share
feel free to do so in the comments below.
Also check out the description below
where we'll provide you some helpful links
for materials and other places you can go
that'll help your understanding or utility of this.
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Until the next time, this is Dirt Farmer Jay
with my new calculator.
