X and Y are two alloys which are prepared by mixing zinc and aluminium in the ratio of 1 : 4 and 11 : 8 respectively. If equal quantities of alloys are melted to form a third alloy Z then what is the ratio of zinc and aluminium in alloy Z?
A boat cover row 12 km upstream in 4 hours and can cover the same distance downstream in 3 hours. What is the speed (in km/hr) of the boat in still water?