The sum of N real numbers (not necessarily unique) is 20. The sum of the 3 smallest of these numbers is 5. The sum of the 3 largest is 7. What is N?

• N = 10
  
  The whole set:
  {1, 2, 2, 2, 2, 2, 2, 2, 2, 3} has 10 members
  
  subset of the three smallest:
  {1 + 2 + 2} sum to 5
  
  subset of the three largest:
  {2 + 2 + 3} sum to 7
  
  remaining memebers of the set:
  {2 + 2 + 2 + 2} sum to 8
• 11 years agoHelpfull: Yes(3) No(0)
• N= 10
  each of smallest 3 = 5/3 = 1.66666.... or numbers are 1.7,1.7 and (1.6 say)
  each of largest 3 = 7/3 = 2.33333.... or 2.3,2.3 and 2.4
  so other numbers lie between 1.7 and 2.3
  say these numbers are 2,2,2,... only.
  number of 2s = (20-7-5)/2 = 8/2=4
  so N = 4+3+3=10
• 11 years agoHelpfull: Yes(0) No(0)