find out the total numbers from 9 to 1000 as the where first digit is lower than the next like (12....not like 21)
1.120
2.219
3.255
4.

• two digit no.s are
  12 to 19, then 23 to 29, then 34 to 39, ..., 78 to 79 then 89
  total 2 digit no.=8+7+6+5+4+3+2+1=36
  
  3 digit numbers
  
  from 100 to 200
  123 to 129, 134 to 139, ..., 178 to 179, 189 , total= 7+6+5+4+3+2+1= 28
  
  from 200 to 300 => 6+5+4+3+2+1=21
  from 300 to 400 => 5+4+3+2+1=15
  from 400 to 500 => 4+3+2+1=10
  from 500 to 600 => 3+2+1=6
  from 600 to 700 => 2+1=3 (678,679 & 689)
  from 700 to 800 => 1 (only 789)
  from 800 to 1000 => 0
  
  total = 1+3+6+10+15+21+28+36 = 120
  
• 10 years agoHelpfull: Yes(45) No(0)
• within 100 such numbers are....8+7+6+5+4+3+2+1=36
  from 100 to 200..................7+6+5+4+3+2+1=28
  from 200 to 300....................6+5+4+3+2+1=21
  from 300 to 400......................5+4+3+2+1=15
  from 400 to 500...................... 4+3+2+1=10
  from 500 to 600...................... 3+2+1=6
  from 600 to 700...................... 2+1=3
  from 700 to 1000...................... 1=1
  total 36+28+21+15+10+6+3+1=120
• 10 years agoHelpfull: Yes(8) No(0)
• ans is.120
• 10 years agoHelpfull: Yes(1) No(0)
• 120 is the right answer
  
• 10 years agoHelpfull: Yes(0) No(0)