The mass of an empty coal truck before it is loaded is 2000 kg.
At the start of a day it is loaded with coal, and the coal makes up 80% of the total mass.
At the first delivery, the driver unloads a quarter of the coal.
Can you express the mass of coal left on the truck, as a percentage of the total mass, after the driver made the first delivery?
This problem is adapted from the World Mathematics Championships