How should I phrase a question that must be answered with an ordinal number (e.g., the third prime)?

Question

I want to make a question having an answer as follows:

5 is the third prime number.

The bold part is the answer. How to phrase the question?

An eternal question about English. :-) We all heard this growing up. (There are expressions in our native languages, equivalent to "how many'th" but grammatical, so this was a natural question to ask.) — ShreevatsaR, Mar 08 '11 at 09:32
If George Washington was the first president, which number is Barack Obama? ... and maybe include instructions on whether to count Grover Cleveland once or twice. — GEdgar, Mar 17 '14 at 15:24
Umm..I'm afraid I'm not looking at it this way. What if the statement is GW was the 1st president of the United States of America, with emphasis on first? — codegasm, Mar 17 '14 at 15:27
English doesn't have a special question word, nor even a good construction, to ask questions specifically about ordinal numbers (first, second, ..., forty-fourth, ...), the way How many? asks about cardinal numbers. If we had a productive morphology, we could ask "*How manyth President is Barack Obama?" But we don't. — John Lawler, Mar 17 '14 at 15:38
Possible duplicate of Framing a question whose answer is an ordinal number — Marthaª, May 27 '16 at 15:42
In which order the 5 became a prime number? In which order the 5 came to a prime number? — Balakrishnan, Feb 01 '18 at 07:38

score 35 · Answer 1 · answered Mar 03 '11 at 20:06

35

FX's answer is an excellent option (and has my vote).

One other technique that is sometimes used in math or science questions is to give an example response as part of the question:

The number two is the first prime number. In the sequence of prime numbers, what is the position of the number five?

This is particularly effective for a verbal question, where using a variable 'n' may be more confusing than it is in print (depending on the audience). One disadvantage is the relative verbosity of this form, but it is mathematically unambiguous while expressly stating the desired form of the answer.

answered Mar 03 '11 at 20:06

robert_x44

1,146

1

I'm curious, why doesn't English have a word for this? Seems a pretty common useful word in our daily lives. Does this problem exist in all Indo-European languages? – Neerkoli Jan 20 '21 at 11:16
1

@WeirdElfB0y No, e.g. German has "Die wievielte Primzahl ist 5?" -- Usefulness and existence of words is not always as correlated as one would wish. English has no single word for the useful concept "the day after tomorrow" and uses exactly that phrase instead, but it does have a single word for the less useful concept "to throw somebody out of the window" – Hagen von Eitzen Jun 30 '21 at 00:10
2

I'm curious, what the word "to throw somebody out of the window"? – insanity May 09 '22 at 06:33

BenOfTomorrow · Answer 2 · 2011-03-03T23:53:23.590

34

Why not simply use the term ordinal directly? For example:

What ordinal number reflects the position of the number five in the set of prime numbers?

or more succinctly:

What is the ordinality of five in the set of prime numbers?

Ordinality might be a bit of a neologism, but the meaning should be clear to anyone familiar with the root, I think.

edited Mar 03 '11 at 23:53

answered Mar 03 '11 at 23:43

BenOfTomorrow

898

1

Among others, I like this answer most. – LaTeX Mar 04 '11 at 00:57
13

Strictly correct, but not a very easy question to understand if by people who are not well educated in mathematics. (Most people I know who don't do science for a living will stop listening to what you say at “ordinal number”, and start thinking hard about what it could possibly mean.) – F'x Mar 04 '11 at 07:59
Yeah. This is probably the best way to answer the question followed by FX's second suggestion. – Dark Star1 Mar 09 '11 at 16:58
@F'x Since this is a math question (it is asking about Ordinal and Prime numbers), how can it be inappropriate to expect knowledge of math to be required to answer it correctly? I guess we are broadening the question to the generic, asking how to get an ordinal number as an answer to any question, math related or not? I'm thinking then, that the question should be edited to reflect this. I'd do it, but not being a regular here, though, I'm not sure I should. – sarah Mar 04 '14 at 02:43

score 25 · Answer 3 · edited Oct 12 '13 at 11:38

25

There is no single, definite, one or two-word answer to that. There is some usage, mostly oral, of constructs like “5 is the how manyth prime number?”, but it is definitely not Standard English.

So, the answer to your question will be to reformulate it. For example, if it were a question to a math test, I would say:

For the sentence “5 is the nth prime number” to be correct, what should be the value of n?

or

5 is the nth prime number. What is the correct value of n?

edited Oct 12 '13 at 11:38

RegDwigнt

97,231

answered Feb 22 '11 at 10:13

F'x

38,736

1

Which one is the correct one? what should be the value of n or what should the value of n be? – LaTeX Feb 22 '11 at 10:21
7

I think both are correct: what should be X? and what should X be? (for X = “the value of n”). However, the longer X is, the clearer the first construct is. – F'x Feb 22 '11 at 10:26
1

Against 20 upvotes, I hesitate to ask, but I wonder how this answer can be correct. The value of n in the examples here would be 5, which is not an ordinal number, and the OP asks for a question form that would require an ordinal number as the answer. No? What am I missing? – sarah Mar 04 '14 at 02:33
@sarah "nth" converts the cardinal n to the ordinal nth. – March Ho Oct 20 '15 at 23:22

score 15 · Answer 4 · answered Mar 04 '11 at 05:30

15

Rephrasing slightly, I'd ask: what is the position of 5 in the sequence of prime numbers?

answered Mar 04 '11 at 05:30

Geoff Canyon

159

Dan Bron · Answer 5 · 2015-06-20T14:18:26.110

8

You could use sequentially, as in

Sequentially, which prime is 5?

However, the term is not completely unambiguous: "Sequentially, which president was Abraham Lincoln?" could legitimately be answered with "Well, he was the one after James Buchanan and before Andrew Johnson"; similarly, as a prime, five is "preceded by 3 and succeeded by 7".

edited Jun 20 '15 at 14:18

answered Aug 25 '14 at 14:22

Dan Bron

28,335
17
99
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score 6 · Answer 6 · answered Mar 04 '11 at 04:40

6

It can be "What is the rank of 5 in prime number series?"

answered Mar 04 '11 at 04:40

Anil Soman

245

score 4 · Answer 7 · answered Mar 09 '11 at 15:03

4

I would phrase it as:

In a list of prime numbers, in which position does 5 appear?

answered Mar 09 '11 at 15:03

score 3 · Answer 8 · answered Mar 03 '11 at 16:15

3

I think you could say:

5 is which prime number?

answered Mar 03 '11 at 16:15

Hellion

59,365

12

An my answer would be, "The one before seven." – Peter Olson Mar 03 '11 at 17:26
10

Without more context, I would not know what form of answer you were looking for. – luqui Mar 07 '11 at 07:51
5

I agree with luqui. If I saw "5 is which prime number?" without context, I'd probably say "Er… 5 is 5. Which other prime number can it be?" – ShreevatsaR Mar 08 '11 at 16:38
2

This could also be answered by "5 is the happy prime number!" Or any other adjective. Not necessarily indicating the position. – mikhailcazi Oct 12 '13 at 11:24
I must join the chorus--the question this answer proposes has too many potential answers and certainly does not lead invariably, or even most frequently, to the sort of answer required by the OP> – sarah Mar 04 '14 at 02:31

score 3 · Answer 9 · answered Mar 09 '11 at 16:34

3

What is the position of n in the series of prime numbers?

answered Mar 09 '11 at 16:34

Yitzchak

1,326

score 2 · Answer 10 · answered Mar 07 '11 at 18:25

2

In the series of primes described using the following constructs, 2 is the first prime number and 3 is the second prime number, what is 5?

answered Mar 07 '11 at 18:25

n0nChun

2,735

Alternatively, "If two is described as 'the first prime number', and three is described as 'the second prime number', how would five be described?" – supercat Oct 15 '12 at 17:59

score 2 · Answer 11 · answered Aug 25 '14 at 13:52

In getting an ordinal response from our kids on quizzes we ask "what is the number-[thing]?", pronounced almost as if it were hyphenated "what number-president is G. W. Bush?". In writing I would be very specific, usually with leading example: "In terms of land area Alaska is first; what is Rhode Island?"

score 1 · Answer 12 · answered Feb 22 '11 at 10:13

1

Whew, I had to read this a few times

In a list of prime numbers, where is the number 5?

answered Feb 22 '11 at 10:13

mplungjan

29,914

The question is asked the other way around (5 is not the answer, but part of the question). – F'x Feb 22 '11 at 10:15
Also, 5 is the third prime number, starting from 2 (1 is usually not considered prime, and if it is, then 5 is the fourth prime number starting from 1). – F'x Feb 22 '11 at 10:16
Right you are. I had to read the question again – mplungjan Feb 22 '11 at 10:17
Jedi you are; in you is the Force. – apaderno Mar 08 '11 at 00:43

score 1 · Answer 13 · edited Mar 10 '11 at 15:20

1

What is the ordinal status of 5 in the set of prime numbers?

sounds a bit too mathematical, huh?

edited Mar 10 '11 at 15:20

F'x

38,736

answered Mar 09 '11 at 17:32

SrJoven · Answer 14 · 2014-09-03T17:57:31.250

The answer nobody gave is because they assume the answer must be given as a sentence. You will want to ask a question that fills in the blank.

The question is usually posed in tests as:

Foo is the ____^{(st/nd/rd/th)} bar.

Either you want the ordinal or you want what the ordinal counts. You can't (effectively) ask for both things without some context. There are many answers to 5 is __. There's only one answer for 5 is the _^{(st/nd/rd/th)} prime number

score 0 · Answer 15 · answered Mar 03 '11 at 16:14

The phrase n...nth is conventionally used for cases like this. In one sentence, the question can concisely be phrased thus:

For what value of n is five the nth prime number?

If you wanted to use words that are not coined by math, you could use a slightly more ambiguous question:

Which term is five on the series of prime numbers?

score 0 · Answer 16 · answered Mar 17 '14 at 15:36

Who is the 44th President of the United States?

Otherwise, the possibilities are infinite.

How many presidents have there been up to the present day, and who is the most recent?

Why is Barack Obama #44 on a list of US Presidents?

You're going to need to narrow down the context.

11qq00 · Answer 17 · 2021-08-30T20:13:20.720

For non-mathematical contexts (e.g. here), phrasing the question as a single sentence that should yield a definitive correct answer ending end with one of "-st,","-nd",or"-th", you could pose the inquiry as

Which numberth {category} is [object]?

; for the mathematical case, you could phrase it as

What is the ordinality of [object] in the {plural of category}?

. Although neither "numberth" nor "ordinality" are widespreadly recognized words (the former less-so than the latter), they nonambiguously convey succinctly the concept for the respetive purpose desired better, I think, than usable alternative phrasings.

Misneac · Answer 18 · 2015-11-14T08:13:51.987

-1

The prime number (N) is equal to the sum total of all prime numbers < N. Which prime number is N in the ordinal ranking of primes?

That's if you want to be a bit mean and confusing.

edited Nov 14 '15 at 08:13

answered Nov 14 '15 at 07:57

Misneac

734

How should I phrase a question that must be answered with an ordinal number (e.g., the third prime)?

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