A king ordered that a golden crown be made for him from 8 kg of gold and 2 kg of silver. The gold smith took away some amount of gold and replaced it by an equal amount of silver and the crown when made, weighed 10 kg. Archimedes knew that under water gold lost 1/20 th of its weight, while silver lost 1/10 th. When the crown was weighed under water, it was 9.25 kg.
How much gold (in kg) was stolen by gold smith?