1) Firstly we need to set up the equations.
"If they plant 240 trees per day, then they will be short by 400 trees."
"If they plant 280 trees per day, they will plant 200 more than planned."
No solve and simultaneously.
Now sub into either or to find out how many trees planned ( )
2) We have
Now use the formula (where s is the speed of the train)
Now because we have metres over second the unit is metre per second
Thus the speed of the train is
Now assuming the width of the pole is negligible and the train has constant speed, the same formula can be used;
Thus the length of the train is