Question

One morning it begins snowing heavily, and continues snowing at a constant rate. At noon a snowplow starts down a long road, clearing the snow as it goes. At 1:00 a second plow starts at the same place and follows the first plow, clearing the snow that has fallen since the first plow passed. At 2:00 the second plow catches up to the first. When did it start snowing?

Answer 1

no way to know.
How much snow was on the ground?
So far, all we know is that it started snowing some time before noon.