Total number of 6-digit numbers in which only one digit of 1,3,5,7 and 9 can be repeated  and all the five digits 1, 3, 5, 7 and 9 appear is:

1,3,5,7,9

          For digit to repeat we have  ${ }^5{C}_1$choice

          And six digits can be arrange in  $\frac{\overline{)6}}{\overline{)2}}$ways

          Hence total such number = $\frac{5\overline{)6}}{\overline{)2}}$