A box contains 20 balls. In how many ways can 8 balls be selected if each ball can be repeated any number of times?

• The number of combinations of n objects taken r at a time is determined by :
  
  C(n, r) = n! / {(n-r)! r!}
  
  ! = means factorial and can be obtained from the calculator or can be done manually.
  
  Example : n! Means : (n × n-1 × n-2 ×...... ×1)
  
  In this case n =20 , r =8
  
  Substituting in the formulae we have :
  
  20!/{(20-8)!8!} = 20!/(12!8!)
  
  This equals to 125970 times.
• 5 years agoHelpfull: Yes(0) No(1)