3)In T.Nagar the building were numbered from 1 to 100.Then how many 1’s will be present in the numbers?
a)18 b)19 c)20 d)21

• 1st Count number of 1s in 10 to 19 because each 10 to 19 have at least one '1' in them -------->
  (19-10)+1 =10 1's, but 11 has two 1's, so we have to add 1--->10+1 = 11 1's in 10 to 19.
  Then count number of 1s in 1,21,...,91. 11 is not included because 11 was already counted above
  there are such 9 1's.
  And lastly count 100----> 1 1's
  
  And Total Answer = 11 + 9 + 1 = 21.
• 9 years agoHelpfull: Yes(13) No(0)
• 21 IS THE ANSWER
  1,10,11,12,13,14,15,16,17,18,19,21,31,41,51,61,71,81,91,100
• 9 years agoHelpfull: Yes(2) No(1)
• 20 is the answer
• 9 years agoHelpfull: Yes(1) No(4)
• 21 is ans
  10
  11
  12
  13
  14
  15
  16
  17
  18
  19
  21
  31
  41
  51
  61
  71
  81
  91
  100
• 9 years agoHelpfull: Yes(1) No(1)
• we can find in how many digits 1 cannot have,we will do this
  1 to 9=8
  10 to 99=72
  hence from 1to 99 there are 8+72=80 digits which do not have 1
  so number having 1 will be 99-80=19
  and 100 digit have 1 itself so total number will be 19+1=20
  20 is the answer
  
  
  
  
  
  
• 9 years agoHelpfull: Yes(1) No(1)
• 21
  1,10,11,12,.......,19,21,31,41,51,61,71,81,91,100
• 9 years agoHelpfull: Yes(1) No(1)
• 1,10,11,21,31,41,51,61,71,81,91,100 =13
  And 12,13,14,15,16,17,18,19=8
  total 1's (13+8)=21
• 9 years agoHelpfull: Yes(0) No(0)
• 20
  1,10,11,....,19,21,31,41,......91,100=20
  
• 9 years agoHelpfull: Yes(0) No(0)