In ΔDEF, G and H are points on side DE and DF respectively. GH is parallel to EF. If G divides DE in the ratio 1:3 and HF is 7.2 cm, find length of DF?
Raja and Kundan together can build a wall in 20 days, Kundan and Mahesh build the same wall in 30 days and Mahesh and Raja can build the same wall in 24 days. In how many days can all the three complete the same wall while working together?