A research lab in Chennai requires 100 mice and 75 sterilized cages for a certain set of laboratory experiments. To identify the mice, the lab has prepared labels with numbers 1 to 100, by combining tags numbered 0 to 9. The SPCA requires that the tags be made of toxin-free material and that the temperature of the cages be maintained at 27 degree Celsius. Also, not more than 2 mice can be caged together and each cage must be at least 2 sq.ft in area. The 5 experiments to be conducted by lab are to be thoroughly documented and performed only after a round of approval by authorities. The approval procedure takes around 48 hours. How many times the tag is numbered '4' used by the lab in numbering these mice?
a) 9 b) 19 c) 20 d) 21

• count as 4,14,24,34,44,54,64,74,84,94 then 40,41,42,43,45,46,47,48,49..so ans is 19
• 13 years agoHelpfull: Yes(18) No(41)
• from 0-9:4-1
  10-20:14-2
  similarly,24,34,44,54,64,74,84,94:total=11(44 taken as twice)
  now we take 40,41,42,43,45,46,47,48,49:total=9
  so ,11=9=20 answer c)20
• 13 years agoHelpfull: Yes(17) No(3)
• we hv 4,14,24,34,54,64,74,84,94=(no o 4s are 9)
  and between 40,41,42,43,45,46,47,48,49=9 4s
  and 44 has 2 4sotal no of 4s are=9+9+2=20 ans
  therefore t
• 10 years agoHelpfull: Yes(2) No(0)
• how the answer would be 20. they have'nt asked about the number 4 count in labels. they asked that Number of times the tag is numbered 4. so from 1-10 labeled mice tag numbered 4 comes only once. like that form 1-100, it comes for 10 times so anwer is 10
• 12 years agoHelpfull: Yes(0) No(6)
• 04,14,24,34,54,64,74,84,94->count the no 4 tags its 11(44 has 2 tags with 4 on it)
  and 40,41,42,43,45,46,47,48,49 -> 9 tags with 4
  total 11+9=20 tags with 4 on it.
  similarly with any number.
• 3 years agoHelpfull: Yes(0) No(0)