Four pipes fill a tank in 15, 20, 30 and 40 hours respectively. The first pipe was opened at 6 am, the second at 8 am, the third at 10 am and the fourth at 12 noon. When will the tank get filled completely ?

A tree has broken from a point and the broken part reaches the ground, making an angle of 4 5 ° with the surface. If the total height of the tree is 50m, what is the approx length of the broken part reaching the ground ?