how many 4-digit odd no.can b formd,such dat evry 3 in d no.is folowd by a 6?????
a.108
b.2592
c.2696
d.2700

• Answer comes out to be close to 108.
  Since, it is an odd number, last digit cannot be 6.
  So, the possibility of 3 at TEN's and UNIT's position is ruled out.Hence, 3 could occupy either THOUSAND's place or HUNDRED's place.
  
  The possible number outcomes are as follows :
  1) 36xx : Now there are 50 odd nos between 601 and 699. hence, total numbers in this case = 50
  2) x36x : here, for every Thousand th place we need to evaluate for digits
  (1-9),
  Eg, 1361-1369 = 5 numbers and so on
  9361-9369 = 5 numbers
  In this case overall, v get 45 numbers.
  So answer is closer to 108 rather than other options.Please suggest a better answer asap.
• 12 years agoHelpfull: Yes(5) No(6)
• @KUMAR CHANDRAJEET Just had a small doubt.Actually, second contition u considered cannot be valid.As, 6 immediately follows a 3 in the number.
• 12 years agoHelpfull: Yes(1) No(5)
• 3 Cases:-
  1st->no. of odd words formed by the arrangement(36--)=1*1*9*4=36
  2nd->no. of odd words formed by the arrangement(-36-)=9*1*1*4=36
  3rd->no. of odd words formed by the arrangement without taking 3,6 pair (----)= 8*9*9*4=2592.
  no other cases r possible because 6 cannot be placed at unit place.
  therefore total no. of words=36+36+2592=2664.(ans)
• 12 years agoHelpfull: Yes(1) No(6)
• 3 will not come at unit place so let us see the possible combination
  possible digits
  3 6 - odd, 9*4=36 word
  3 - 6 odd, 10*4=40 word
  - 3 6 odd, 9*4=36 word
  - - - odd, 8*9*9*4=2592 word
  so toatal word =36+40+36+2592=2704 ans
  
• 12 years agoHelpfull: Yes(0) No(10)