More questions to ponder... Solutions

1. 1 km = 1000m = 1, 000, 000 mm

2. 180m (With 10 posts there are only 9 gaps between posts.)

3. 79  - Between 1 and 100 there are 98 numbers and 19 of those numbers have a 9 in them so there are 79 numbers which do not have a nine.