Two contractors will jointly pave a road, each working from one end. If one of them paves 2/5 of the road and the other 81 km remaining, the length of that road is
The length of the road is 54 km. So you know the 3/5 of the paved road is 81 km and the whole paved road (5/5) is 135 km. 2/5 of the paved road is 135 km minus 81 km is 54 km. If you have any more questions, just comment! :)
