how many three digit number are thre in which if one digit is 3 then it must be follwed by 7 . repetetion is not allowed
a 466
b 463
c 14
d 17

• here we have two possibilities... first 3 7 _ (as 3 should be followed by 7) last place can be filled with 8 ways (0,1,2,4,5,6,8,9 as repetition is not allowed) thus there can be 8 numbers ,, Secondly _ 3 7 here first plce cn b filled with 7 ways (1,2,4,5,6,8,9) as frst digit cant be zero .... thus adding both we get 15 as the answer plzz help me wr i m wrng
• 10 years agoHelpfull: Yes(5) No(2)
• ans is 17 ... because for 1 case 37_ (after 3 and 7 the possible nos are 0,1,2,4,5,6,8,9 hence total 8 numbers ) ... for second case _37 ( the possible no are 1,2,4,5,6,8,9 hence total 7 numbers ) by both the possibilities is 15 ......
• 10 years agoHelpfull: Yes(2) No(0)
• here we hav to count the total 3 digits number ,,, as if it contains 3 den it shud followed by 7 else if no 3 den no 7 so the total 3 digit numbers without 3 and 7 is _ _ _ 8*8*7 (as 0 can aso be included but not for the frst place) so it gives 448 + 15 ( the number containing 3 and followed by 7) thus the total is 463 option b
• 10 years agoHelpfull: Yes(1) No(1)