Just a quick maths question

[LeedsRhodesy]

I'd be grateful if someone could help me out with this.

In a tournament with 100 entrants how many matches would be required in total for everyone to play everyone else once?

x=     n²   -    n
               2

where x= Total number of matches required
          n= Number of entrants

X= 7

[Free_Rollin]

This is essentially the handshake problem. Solution is as pawprint mentioned, which means 4950 matches.

[kukushkin88]

ty, much obliged

[paulhouk03]

you can work this out on a scientific calaulator

i think its the ncr button

[david3103]

Sum of the digits problem - guy 1 has 99 matches, 2 has 98 etc so it's the sum of the digits to 99?

n(n+1)/2
99(100)/2

4950

[Simon Galloway]

you can work this out on a scientific calaulator

i think its the ncr button

You can, but you don't really need to when one of the numbers is small.  in this example, your ncr button is performing this calculation:  100!/(98!2!) which simply cancels down to [(100*99)/2]