Question 1003336
 Ivan drives to the metro station each morning and just to catch his train.
 He drives at an average speed of 30 miles per hour.
 Unfortunately this morning, there was a lot of traffic.
 At the halfway point Ivan found that he had averaged only 15 miles per hour.
 How fast must Ivan drive for the rest of the way to catch his train?
:
2d = the distance to the station
then
2d/30 = the normal time for the trip
let s = the speed required for the last half of the trip
Write a time equation
{{{d/15}}} + {{{d/s}}} = {{{(2d)/30}}}
reduce the 3rd fraction
{{{d/15}}} + {{{d/s}}} = {{{d/15}}}
It's obvious from this equation that it's impossible for him to catch his train