Concept:A permutation is an arrangement of objects in a definite order.\(\displaystyle ^n P_r=\frac{n !}{(n-r) !}\),where, nPr = Permutation n = total number of objects r = number of objects selectedCalculation:Numbers between 300 and 400 consist of three digits with the digit at hundreds place equal to 3.Since repetition is not allowed and there must be only odd numbers, ones places can be filled using the digits 1,5,7 and 9 in 4P1 ways. Now tens place can be filled by using any digits except the digit at one's and hundred's place in 8P1 ways. Hence, the required number of numbers = 4P1 × 8P1 = 4 × 8 = 32.? The Total numbers between 300 and 400 in which none of the digits is repeated are 32.