Help me recognize these?

7eot5x

New member
Joined
Jan 31, 2020
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2
Hey guys I have a few really easy silly questions if you wouldn't mind helping me out. Hopefully these questions fall under the correct mathematical category if it doesn't I apologize and will try to move it.

1. Are these two the same?

6-5/8"

and

6 5/8"

Wondering why the dash is used or is it just another way to write it out? Are both of these six and five eighth inches?


2. What is this?

3/4-1"?

Is this the same as 1-3/4" How would you pronounce that?


3. Is this [three and five eighth inches width x four and five eighth inches height x eight feet zero inches length? Width always comes before height correct?

3-5/8” x 4-5/8” x 8’-0”


4. Last question, is this pronounced two point 1 (2.1) inches x four point zero four (4.04) inches?

2.10” X 4.04”


Thanks guys!!
 

Dr.Peterson

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Nov 12, 2017
Messages
6,203
The dashes would never be used for any of these within a math class, as they would be read as subtraction. But these notations seem to be common in the business world.
  1. 6-5/8" just means 6 5/8", that is, 6 and 5/8 inches. I don't know why they do it, but presumably it makes them feel it is more clearly a single (mixed) number. I'd call it a mistake, but a common one in some fields.
  2. What is 3/4-1"? I need to see the context. I've never seen a mixed number written that way; my first impression is that it might mean 3/4" to 1", not a single number but a range. If I'm right, then this is a third meaning for the hyphen, which can get really confusing!
  3. The order of dimensions is not universal; for a given type of product there is often a typical ordering, but that will be different for, say, luggage, furniture, and boxes.
  4. Yes, contrary to what teachers tends to say, 2.10” X 4.04” is typically read as "two point one inches by 4 point zero four inches", rather than "two and ten hundredths by four and four hundredths inches". The former is efficient for reading and writing, while the latter requires thinking, which is error-prone.
 

HallsofIvy

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Jan 27, 2012
Messages
5,641
Hey guys I have a few really easy silly questions if you wouldn't mind helping me out. Hopefully these questions fall under the correct mathematical category if it doesn't I apologize and will try to move it.

1. Are these two the same?

6-5/8"

and

6 5/8"

Wondering why the dash is used or is it just another way to write it out? Are both of these six and five eighth inches?
Yes, those are the same. Sometimes the - is used in order to avoid confusion with 65 inches. You could also write "6 and 5/8 inches" to mean the same thing.

2. What is this?

3/4-1"?

Is this the same as 1-3/4" How would you pronounce that?
I have never seen that before. Is it a measurement? Please show us what the exact statement of the problem was.

3. Is this [three and five eighth inches width x four and five eighth inches height x eight feet zero inches length? Width always comes before height correct?

3-5/8” x 4-5/8” x 8’-0”
How do you distinguish between "height" and "width"? The distinction is basically arbitrary.

4. Last question, is this pronounced two point 1 (2.1) inches x four point zero four (4.04) inches?

2.10” X 4.04”
Yes, you can say "two point one" or "two and one tenth".

Thanks guys!!
 

JeffM

Elite Member
Joined
Sep 14, 2012
Messages
4,333
We prefer that you write one question per thread. Otherwise things quickly get confusing.

With respect to your first question, it depends. It is NOT STANDARD in mathematics to write a "mixed fraction" with a dash. If you saw this in a math text, it would mean to subtract 5/8ths of an inch from 6 inches because the dash mark always means minus. If it is not a math text, it should not be used to indicate a mixed fraction, but who knows what people may do.

With respect to 3/4 - 1, that means to subtract 1 from 3/4 under any normal math reading.

In the third one, your are dealing with three dimensions, length, height, and depth. I do not know whether there is a standard order in which those are given. If so, it is not a math convention. And the x is read "by" rather than "times."
 

firemath

Full Member
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Oct 29, 2019
Messages
388
On your third question, should it be written like this:

\(\displaystyle 3/4"-1"\)

instead of:

\(\displaystyle 3/4-1"\)?
 

7eot5x

New member
Joined
Jan 31, 2020
Messages
2
On your third question, should it be written like this:

\(\displaystyle 3/4"-1"\)

instead of:

\(\displaystyle 3/4-1"\)?
I think so, I appreciate the help from all of you guys. I was talking to someone about drilling a hole and they wrote that down and I was confused. Turns out he probably wrote it down wrong and the correct way is the way you mentioned. Much appreciated for all of you guys!
 

firemath

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Oct 29, 2019
Messages
388
On the note of your pronunciation of decimal numbers, one would not say "point" if one wanted to be absolutely correct.
As @HallsofIvy said, "two and one tenth" is more correct.
 

tkhunny

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Staff member
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Apr 12, 2005
Messages
10,454
With respect to 3/4 - 1, that means to subtract 1 from 3/4 under any normal math reading.
Just a tiny note from the ancient times...

In the world of logarithm tables, one might find a mantissa and characteristic with opposite signs. Of course, this is quite awkward to write. Adjustments normally would be made.
 

firemath

Full Member
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Oct 29, 2019
Messages
388
One more thing............

Hey guys I have a few really easy silly questions........
No question is silly if you really want the answer! :)
 
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