1.35. Four people are on a grass-covered island. A
fire burns from one end of the island to the other, but no one gets severely
1.35 answer: The fire is slow moving and the four are able to “back
burn” by starting a new fire on the other side of them. When an area is
burnt off, they can safely stand on the burnt patch, as it now contains no
fuel for the grass fire. This is an actual technique used in Australian
bushfires (and, I think, elsewhere).