Ten boxes are there. Each ball weighs 100 gms. One ball is weighing 90 gms.
i) If there are 3 balls (n=3) in each box, how many times will it take to find 90 gms ball?
ii) with n=10
iii) with n=9

• for n=3:
  
  select 1 ball from 3 balls and check weight => 3c1=3 ways
  there are 10 boxes so 3*10=30 times .
• 12 years agoHelpfull: Yes(6) No(3)
• 1)each box has 3 balls.so weigh all the 10 boxes. 1 box is lesser in weight which has 90 gm ball---> 10 ways
  then the box has 3 balls.weigh each ball--> 3 ways
  so total ways--> 13
  2)in a similar way--> 10+10=20 ways
  3)10+9=19 ways
• 10 years agoHelpfull: Yes(5) No(1)
• by using balance we can find it faster
  among 10 boxes which weighs more we will need to check 3 times
  5-5
  2-2 or 1
  1-1
  i.e 5 boxes on one side while 5 boxes on other side
  side which contains 90gm box will have less weight
  and go up
  in such a way
  the ans is
  i)"4" for 10box 3 balls in each
  ii)"6" for 10box 10 balls in each
  iii)"6" for 10box 9 balls in each
• 10 years agoHelpfull: Yes(1) No(0)
• Total 3 times for n=3
• 9 years agoHelpfull: Yes(0) No(0)