A scale of 1:125000 means that for any length that is on the map, the real life length is 125000 times as long. This also means that for any length in real life, the length on the map is 1/125000 times as long.
So, a real life length of 10km will be represented by a map length of 10km/125000 = 0.00008km = 8cm
When you have to find the length of map to the actual distance, you will multiply. and if its the other way around as in finding the distance on the map, you will divide. in this case, we will be diving as it is asking the distance on the map.
a scale will always have the unit centimeter, so we will be converting 10km into centimeter.