For this, we must ensure that the last digit (8th digit) is odd, which means it can only be $1,3,7,5$ or 9 and first digit can't be zero.
$\therefore$ The total no. of 8-digit odd numbers.
$=($ Choices for first digit $) \times($ Choices for the remaining 6 digits) $\times$ Choices for the last digit.
$=9 \times 10^6 \times 5=45 \times 10^6$