Question 392593

less then 1000 means upto 3 digit numbers and at unit place either 0 or 5.


Single digit numbers......  only 5  i.e  no. of ways = 1


Two digit numbers...

          when 0 on unit place , no. of ways = 9
             
           when 5 on unit place, no. of ways = 8
                                  
                         total no. of ways for 2 digit = 17 


Three digit numbers..
         
        when 0 on unit place , no. of ways 9P2 = 9*8 = 72 
         
          when 5 on unit place, no. of ways  = 9P2 - 8 = 64
    ( in 8 numbers 0 will be on first place, so discard it)

                      total no. of ways for 3 digit = 136




                  total no. of ways =  1 + 17 + 136 = 154