AILET 2019 BA LLB Question Paper with answer key for online practice

A water tank has eight pipes fitted into it. Pipes are of two types: Green Pipe and Red Pipe. Green pipes are used to fill the tank and the Red pipes are used to empty the tank. Every Green pipe can fill the tank in 12 hours and every Red pipe can empty it in 36 hours. On opening all the pipes an empty tank is filled in 3 hours. The number of Red pipe is