A certain number of men agreed to do a work in 20 days. 5 men did not come for work. Others completed the work in 40 days. Find the number of men who had agreed to do the work originally.
A ball, thrown vertically upward, rises to a height of 80 m and returns to its original position. The magnitude of its displacement after 7 s of motion will be ____. (take g = 10 m/s2)