Probabilities question

  • Thread starter cdux
  • Start date
  • #1
188
0
That's not exactly coursework (it's studying) but I've spammed the probabilities forum too much.

Can someone explain this part?

Knowing that P(k)=P(X=k)=c(101-k)

For a 'turtle' that can live up to 100 years, find 'c'.

And it goes

K2Vwoxp.png


I don't understand the jump from cΣk to c100(100+1)/2
 

Answers and Replies

  • #2
DrClaude
Mentor
7,607
4,009
$$
\sum_{k=1}^n k = (1+n) \frac{n}{2}
$$
To see how to get the formula, list the numbers of the sum, then sum the first with the last, the second with the second to last, etc.
 
  • #3
188
0
then sum the first with the last, the second with the second to last, etc.
Ah, hacky. I was expecting a more straightforward way.

Thank you!
 

Related Threads on Probabilities question

  • Last Post
Replies
2
Views
840
  • Last Post
2
Replies
30
Views
3K
  • Last Post
Replies
15
Views
2K
  • Last Post
Replies
2
Views
1K
  • Last Post
Replies
6
Views
1K
  • Last Post
Replies
11
Views
2K
  • Last Post
Replies
10
Views
2K
  • Last Post
Replies
3
Views
916
  • Last Post
Replies
6
Views
921
  • Last Post
Replies
11
Views
929
Top