MATH371 First Four Weeks
Lec 1 Q1. How many three-digit integers there are so that the sum of the three digits is 24 where all the digits are distinct? Simple if we split the number in certain order, say, dictionary order and descending order.., $$ 24 = 9+8+7 $$ and we can’t do anything more, It should be $3!=6$ Q2. How many three-digit integers there are so that the sum of the three digits is 18 where all the digits are distinct ...