25 persons can complete a work in 60 days. They started the work. 10 persons left the work after x days. If the whole work was completed in 80 days, then what is the value of x ?
The angle of elevation of the top of a chimney and roof of the building from a point on the ground are x and 45° respectively. The height of buidling is h metre. Then the height of the chimney,(in metre) is