# How to read the fraction 4/21?

#### emma.learns

##### Senior Member
Dear all,

How should I read 4/21 when the denominator is 21?

Is it four twenty-first or four twenty-firsts?

I know we can say four over twenty-one but I'd also like to know some other ways to read the fraction.

Thank you!

• #### ewie

##### Senior Member
Four twenty-firsts. (That's a very weird fraction)

#### Lun-14

##### Banned
Four twenty-firsts. (That's a very weird fraction)

#### Lun-14

##### Banned
A/one fifth.
How would you read it?
A [pause] one fifth
A over one fifth
A by one fifth
Four twenties

#### heypresto

##### Senior Member
Either 'a fifth' or 'one fifth'.

Or 'four twentieths'. But this is unlikely, as it's unlikely anyone would write the fraction '4/20', without further reducing it to '1/5'.

#### natkretep

##### Moderato con anima (English Only)
If you're reading it as a fraction, you need to use the ordinal for the denominator: one fifth, two tenths, four twentieths.

If you're reading it the way it's written, you can use the cardinal: one over five, two over ten, four over twenty.

#### Lun-14

##### Banned
Either 'a fifth' or 'one fifth'.

Or 'four twentieths'. But this is unlikely, as it's unlikely anyone would write the fraction '4/20', without further reducing it to '1/5'.
What would you say about my four suggestions in #5 - are they correct?

#### Retired-teacher

##### Senior Member
The fact that 4/20 = 1/5 is not really relevant. There may be a problem where changing 1/5 into 4/20 is useful. I would call this four twentieths.

4/21 is not so easy. "Four twenty firsts" sounds wrong, so I think I would say "four twenty oneths" even though that sounds ridiculous.

#### natkretep

##### Moderato con anima (English Only)
What would you say about my four suggestions in #5 - are they correct?
It should be obvious from the suggestions we have been giving that the examples in Post 5 are incorrect.

#### semeeran

##### Senior Member
I read 4/21 as four by twenty one.
Is it OK?
Thanks.

#### sound shift

##### Senior Member
4/21 would not be read as "four by twenty-one" in the UK.

#### Lun-14

##### Banned
4/21 would not be read as "four by twenty-one" in the UK.
How is it read in the UK?

#### kentix

##### Senior Member
In your comment #5 you misunderstood what he wrote.

A/one fifth.

He meant you could use A or you could use one in front of fifth. Your choice. You read it all together as one thing.

#### kentix

##### Senior Member
Four twenty firsts" sounds wrong, so I think I would say "four twenty oneths" even though that sounds ridiculous.
In the U.S. we would definitely say four twenty-firsts.

We would definitely not say 4 by 21. Those would be the dimensions of a rectangle.

#### Barque

##### Senior Member
If you're reading it the way it's written, you can use the cardinal: one over five, two over ten, four over twenty.
The usual Indian English way of saying it is with "by" instead of "over", which explains Semeeran's question. (By is short for divided by.)

#### Lun-14

##### Banned
See post #2.
I see. Thanks.
Do you also read "4/21" as "four over twenty-one" in BE?

Is the use of "by" and "over" equally common in BE?
Thanks.

#### Packard

##### Senior Member
I see. Thanks.
Do you also read "4/21" as "four over twenty-one" in BE?
If it were a common fraction we (USA) would say:

• Three sixteenths
• Five thirty-seconds
• nine sixty-fourths
• etc.

But for 4/21 it would be awkward to say "four twenty-firsts" (better than "four twenty-oneths.")

If I were pressed to use the fraction then I would also say "four over twenty-one", though in a sentence it really does not work.

What is the size of the screw you are using?

It's a four over twenty-one.

The above sounds really weird to me, versus below which sounds fine:

What is the size of the screw you are using?

It's a three sixteenths.

#### Andygc

##### Senior Member
Do you also read "4/21" as "four over twenty-one" in BE?
That's possible. But it is a very unusual fraction. I cannot ever remember dividing anything into twenty-firsts. I have rules that measure twentieths, twenty-fourths and thirty-seconds of an inch, but I've never seen one that can measure twenty-firsts.

#### Glenfarclas

##### Senior Member
That's possible. But it is a very unusual fraction. I cannot ever remember dividing anything into twenty-firsts. I have rules that measure twentieths, twenty-fourths and thirty-seconds of an inch, but I've never seen one that can measure twenty-firsts.
It presumably wouldn't arise from a measurement system, but rather from some formula like a²/(b*c), in a particular situation where a=2, b=7, and c=3.

And I can't really imagine saying it any way other than "four over twenty-one."

#### Packard

##### Senior Member
It presumably wouldn't arise from a measurement system, but rather from some formula like a²/(b*c), in a particular situation where a=2, b=7, and c=3.

And I can't really imagine saying it any way other than "four over twenty-one."
It is a meaningless measurement. You have the "4/21". What do you do with it? You cannot measure it or transfer it to another surface or product. So if you don't convert it to decimal equivalent (inches or metric) it is just a number and not a usable measurement.

What size do you need me to cut this plywood to?

14 inches and 4/21".

And how do I measure that?

What? You don't have a 21th measuring tape? What kind of carpenter are you?

#### Glenfarclas

##### Senior Member
It is a meaningless measurement.
Who ever said it has to be a measurement in the first place? It could be the first derivative of some curve.

#### Packard

##### Senior Member
Who ever said it has to be a measurement in the first place? It could be the first derivative of some curve.
OK. I deal with measurements. This may work for other fields.

#### kentix

##### Senior Member
In pure math you run into fractions of all kinds. You have to pronounce them whether they are used to measure anything or not.

4/932 = four nine-hundred and thirty-seconds

And I can't really imagine saying it any way other than "four over twenty-one."
And I speak American English also and can't ever imagine saying it that way. Do you have a math background?

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#### Glenfarclas

##### Senior Member
And I speak American English also and can't ever imagine saying it that way. Do you have a math background?
Yes, I majored in it.

#### kentix

##### Senior Member
I wasn't a math major but took a lot of high level college math (very near Chicago) and can't recall ever hearing people using that form. Granted, you don't talk about a lot of specific fractions in college level math.

How would you say this problem out loud?

5/6 + 4/21 =

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#### Dale Texas

##### Senior Member
It presumably wouldn't arise from a measurement system, but rather from some formula like a²/(b*c), in a particular situation where a=2, b=7, and c=3.

And I can't really imagine saying it any way other than "four over twenty-one."
That's how I'd say it too in this context of already knowing we're talking about fractions.

#### emma.learns

##### Senior Member
Thank you all for the input

#### RM1(SS)

##### Senior Member
4/21 is not so easy. "Four twenty firsts" sounds wrong, so I think I would say "four twenty oneths" even though that sounds ridiculous.
Ditto.
We would definitely not say 4 by 21. Those would be the dimensions of a rectangle.
Or a multiplication problem.

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