Question

Pipe 'a' can fill a tank in 20 minutes. pipe'a' and 'b' both are opened and after 6 minutes pipe 'a' is closed and pipe 'b' takes 15 minutes to fill the tank. in how many minutes, can pipe 'b' fill the tank?



a. 33



b. 30



c. 28



d. 35

Answer 1

I am doing it mentally and I think it's c