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
Pick:
A) 466  B) 463  C) 14  D) 17  E) 18
1st case: three digits no without considering 3   first place can be filled using 8 numbers (excluding 0 and 3)=8   second place can be filled using 8 numbers (excluding 3 and digit filled in first place)=8   last place can be filled using 7 numbers (excluding 3 and digit filled in first place &amp; second place)=7   therefore, three digits formed are= 8*8*7= 
<gadget id="calculator">8*8*7</gadget>
<output>448</output>
448   2nd case: now consider number using 3   if 3 and 7 are first two digit then last digit can be filled using 8 digits   if 3 and 7 are last two digits then first place can be filled using 7 digits   therefore, total 3 digit no including 3 are= 8+7= 
<gadget id="calculator">8+7</gadget>
<output>15</output>
15   hence, total 3 digits numbers are= 448+15= 
<gadget id="calculator">448+15</gadget>
<output>463</output>
463   ANSWER:463
<result>B</result>
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