KöMaL 2015 K485

Tom Thumb and the giant arrive at the castle of the dragon. Although the giant is 3.5 metres taller than Tom, he still cannot reach the top of the castle wall when he stands on the ground. So he lifts Tom Thumb on his palm over his head. Tom can just climb the wall, which is 6 metres and 20 centimetres high. The giant has long hands: he can reach 40% of his height above the top of his head, while Tom can only reach 20% of his height above the top of his head. How tall is the giant, and how tall is Tom Thumb?