Question

One pump can fill a tank with oil in 10 hours. Together with a second pump, it can fill the tank in 6 hours. How long will it take the second pump to fill the tank if it is used alone?

Answer 1

in one hour, it will fill 1/10
how much will be filled if both work together?
\[\frac{ 1 }{ 10 }+\frac{ 1 }{x }=\frac{ 1 }{6 }\]
solve for x

Answer 2

Add the rates.