Two trains are moving in opposite directions with the same speed. If the length of each train is 120 metres and they cross each other in 12 seconds, then what is the speed (in km/hr) of each train?
A work can be completed by 18 boys in 24 days. If 6 boys leave after working for 12 days, then how many days will be needed to complete the remaining work?
If the volumes of two right circular cones are in the ratio 1:4 and their diameters of bases in the ratio 4:5, then their heights will be in the ratio: