floor of Room of TIPU is made of square tiles 1m sq. each .Diagonal tiles are BLACK and rest are WHITE .Er. Vesvesvaraya notice that some group of the number of black tiles are count wrongly . 101,111,121,131,141. how many tiles of the above numbers are wrong?

• given that floor is square
  so consider it as nxn matrix
  so if 'n' is odd then there are 2n-1 diagonal squares
  if 'n' is even then there are 2n diagonal squares
  clearly if n is odd then in contains odd num of diagonals
  so given all num's are odd
  so 2*n-1 = 101 -> n = 51 odd RIGHT
  2*n-1 = 111 -> n = 56 even WRONG
  2*n-1 = 121 -> n = 61 odd RIGHT
  2*n-1 = 131 -> n = 66 even WRONG
  2*n-1 = 141 -> n = 71 odd RIGHT
  SO 2 NUM'S 111 AND 131 ARE WRONG
• 11 years agoHelpfull: Yes(17) No(0)
• 111 and 131 (total of 2) will be counted wrong beacuse...
  case 1 for m*n there can't be square tiles place....
  so m*n should be eual ...ie m=m ...Draw fig in ur rough and find out why..
  
  if n=odd diagonal tiles =2n-1 so here 101,121,141 satisft the condn
  
  for n= even diagonal tiles = 2n no case here..
  so 131 n 111 fails any condn here ....
  
  check these results by sketching grids on pages of 2*2 3*3 4*4 5*5 it will jsutify ur answers..Good luck
• 11 years agoHelpfull: Yes(4) No(0)
• answer is 111, 131, This two number are counted wrongly....
  make the odd number of matrix. e.g. 3x3,5x5,7x7 has diagonal tiles are 5,9,13 respectively .... and so on....where you get 51x51=101 diagonal black tiles... so this count exist.. but above 111,131 dosent come in the sequence...
• 11 years agoHelpfull: Yes(2) No(0)
• not getting the ques.
• 11 years agoHelpfull: Yes(0) No(0)
• question is ambiguous
• 11 years agoHelpfull: Yes(0) No(0)