An oil tanker can be emptied by the main pump in 4 hours. An auxiliary pump can empty the tanker in 7 hours. If the main pump is started at 5 PM​, when should the auxiliary pump be started so that the tanker is emptied by 8 PM​?

Respuesta :

Answer: 1:00

Step-by-step explanation: if you start at 12:00 then you finish at 7:00 if you start at 1:00 then both finish by 8:00