Find the sum of the First $50$ Natural Numbers starting from $11$. Is it from $11-50$ or $11-60$? This a simple question yet confusing for me, I found the answer as 1220 by taking sum from $11$ to $50$, by inferring the question as first 50 natural numbers {$1,2,3,4,5,6,7,8,9,10,11,...49,50$} 
and sum starting from 11 which means sum $= 11+12+...+49+50$. 
But my friend says otherwise, he took from 11 to 60 and says answer as 1775. Can anyone explain how to infer the word first in the context of maths.
 A: I think there's a bit of ambiguity in the language, so either interpretation is justified. I also think it's just a poorly worded question. The only recourse is to ask whoever set the question or to just let it go - I don't think the intended meaning is really something you can figure out by yourself.
To clarify why I believe both interpretations are valid:


*

*"The first $50$ natural numbers" means $1-50$. So then "The first $50$ natural numbers (starting from $11$)" could mean the same set $1-50$ but starting from $11$ and excluding $1-10$. So $11-50$.

*"The natural numbers starting from $11$" means $11,12,\ldots$. So then "(The first $50$) natural numbers starting from $11$" could mean the first $50$ elements of this set. So $11-60$.
A: From a book for GRE practice
I can see how the word "first" is used in a particular context in mathematics. Is that why my interpretation is wrong... or is that my interpretation does not bring logic even by english, that's what i would like to know.. thanks @jam now i know i am not alone in this. 
 Take a look at the image link attached here, if we see the options everyone will surely come to conclusion my friend is right.. but i wanted to clarify if there is any logical mistake in my interpretation.
A: Following the link that you provided, we find that the wording in the review book is

Find the sum of first $50$ natural numbers starting from $11$.

This is not Standard English; it should say "of the first" rather than "of first". Hence I have some doubts that you will ever see a question worded exactly like this on an actual GRE exam.
But if the phrase "the first $50$ natural numbers starting from $11$" were to occur on an actual GRE, I probably would interpret it by considering the
"natural numbers starting from $11$" (which are $\{11, 12, 13, \ldots\}$) and then taking the first $50$ of those.
That is, I would take
the first $50$ members of $\{n \in \mathbb N \mid n \geq 11\}.$
The alternative, if I first collect the first $50$ natural numbers and then "[start] from $11$", is that the "starting from $11$" part becomes meaningless. I already have a finite set of $50$ numbers, so what does it matter any more where the set "starts"?
If I write $\{11,12,13,\ldots,49,50,1,2,3,\ldots,9,10\},$
it means exactly the same thing as  $\{1,2,3,\ldots,49,50\}.$
The "starting" point of the sum of a finite set is just as meaningless,
since addition is commutative.
This logic does not prove that my interpretation is correct--I believe the wording is ambiguous--but I find the other interpretation a highly unnatural use of the natural English language.
A: The question says to calculate the sum of 50 natural numbers from 11 , it doesn't mean that to calculate the sum of natural numbers from 11 to 50 . So there is an high school equation to calculate this its is
Sn = n/2 (2f+ (n -1)d)
S - sum of natural numbers
n - no. Of terms ( eg: in this situations we are going to calculate the
sum of 50 terms)
f - First term ( eg : here 11 is the first term because we are adding the
natural numbers starting frm 11)
(n - 1) - we have to subtract 1 from the no. Of terms .( eg: here no. Of
terms we are going to add is 50 , so we need to subtract 1
from it (50 - 1) and we get 49 )
d   - it is the commen difference between terms ( here the first term is
11 and 2nd term will be 12 . So difference between terms is 12-
11=1)
Therefore ans;
S50 = 50 /2( 2×11+49×1)
=25(22+49)
= 25 × 71
= 1775
A: There's a high school formula for the sum of consecutive terms in an arithmetic sequence: it is equal to the number of terms, times the arithmetic mean of the first and last term.
Here the first term is $11$ and $50$th term  is $60$, so the sum is
$$50\times\frac{11+60}2=1775.$$
