Combination and summation notation.

Click For Summary
The discussion centers on understanding the notation for summation and combinations. The user is confused about interpreting the summation \sum (i/k) from i=0 to n and whether it can be expressed as (0/k)+(1/k)+(2/k)...(n/k). They express uncertainty about the implications when n is less than k, noting that this leads to negative factorials, which are undefined. The conversation highlights the need for clarity in mathematical notation and the rules governing combinations. Overall, the user seeks guidance on proper interpretation and calculation methods in these scenarios.
EV33
Messages
192
Reaction score
0

Homework Statement


I am having trouble reading this notation

\sum (i/k)

The sum is from i=0 to n

I wasn't sure how to write the combination of i,k on the computer so I just wrote it as i/k.


Homework Equations


When I say combination I am talking about this formula n!/(k!(n-k)!)


The Attempt at a Solution



Is this just (0/k)+(1/k)+(2/k)...(n/k)

I am sure I am interpeting it wrong but If I am not what do you do for situations where n is less than k because when you do the combination you get n!/(k!(n-k)!), and I don't think it is possible to do a negative factorial.
 
Physics news on Phys.org
I don't think 'n' can be less than 'k' for the reason you said.
 
Question: A clock's minute hand has length 4 and its hour hand has length 3. What is the distance between the tips at the moment when it is increasing most rapidly?(Putnam Exam Question) Answer: Making assumption that both the hands moves at constant angular velocities, the answer is ## \sqrt{7} .## But don't you think this assumption is somewhat doubtful and wrong?

Similar threads

  • · Replies 7 ·
Replies
7
Views
2K
Replies
1
Views
1K
  • · Replies 22 ·
Replies
22
Views
898
  • · Replies 1 ·
Replies
1
Views
1K
  • · Replies 1 ·
Replies
1
Views
1K
  • · Replies 18 ·
Replies
18
Views
2K
Replies
1
Views
1K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 4 ·
Replies
4
Views
2K
Replies
17
Views
2K