1 km = 1000 m so 824 km = 824*1000 = 824000 metres. Simple!
There are 100/0.1 = 1000 decimetres in one hectometre. Therefore, 824 hectometres is equal to 824 x 1000 = 824000 decimetres.
The GCF is 1000.
The GCF is 2.
The GCF is 1.
The GCF is 1.
The GCF is 1.
The GCF is 50.
The GCF is 100.
The GCF is 125.
The GCF is 1.
The GCF is 8.