# math

posted by .

a tank can be filled by one pipe in 3
.5 hours and emptied by another in 4.2 hours.if both ipes are running, how long will it take to fill an empty tank?

• math -

in work problems like this, think of the amount of work each person can do in the unit of time.

if pipe a can fill the tank in 3.5 hours, then in one hour it can fill 1/3.5 of the tank.

The other pipe b can fill 1/4.2 of the tank in one hour.

So, in one hour, both pipes working together can fill up

1/3.5 + 1/4.2 = 0.5238 of the tank

So, to fill the whole tank, it will take 1/.5328 hours, or 1.90909 = 1 10/11 hours

In general, if various workers can do the job in a,b,c,... units of time, then working together they can do it in n units of time:

1/n = 1/a + 1/b + 1/c + ...

• math -

I see I misread the problem. It was answered correctly later on

## Similar Questions

1. ### math

the fill pipe for a tank can fill the tank in 4 hours and the drain pipe can drain in 2 hours. If both pipes are accidentally opened, how long will it take to empty a half-filled tank?
2. ### college algebra

an inlet pipe can fill a large water tank in 3 hours. an outlet pipe can empty the same tank in 5 hours. given an empty tank, at 8pm, activate both pipes. what time on the clock will it be before the tank is completely filled?
3. ### math

A tank fitted with two pipes is to filled with water. One pipe can fill it in 5 hours. After it has been open for 3 hours, the second pipe is opened and the tank is filled in 4 hours more. How long it would take the second pipe alone …
4. ### math

a tank can be filled by one pipe in 3.5 hours and emptied by another in 4.2 hours. if both pipes are running, how long will take to fill an empty tank ?
5. ### maths

a tank can be filled by one pipe in 3.5 hours and emptied by another in 4.2 hours. if both pipes are running, how long will take to fill an empty tank ?
6. ### maths

a tank can be filled by one pipe in 3.5 hours and emptied by another in 4.2 hours. if both pipes are running, how long will take to fill an empty tank ?
7. ### algebra

a tank used to operate equipment can be filled with air in 3 hours. when the outlet valve is open, the same tank can be emptied in 5 hours. if the tank is filled with the outlet valve open approximately how long will it take to fill …
8. ### Math

One pipe fills a tank in 1 hour while another pipe can fill the same tank in 2 hours. How long will it take to fill the tank if both pipes are used.
9. ### Math

A tank is filled with an intake pipe that will fill it in 5 hours and an outlet pipe that will empty it in 15 hours. If both pipes are left open, how long will it take to fill the empty tank?
10. ### Algebra

) An inlet pipe can fill an empty tank in 5 hours by itself, and an outlet pipe can drain the same tank when full in 7 hours by itself. If the tank is two-thirds full when the valves for both pipes are opened, how many minutes will …

More Similar Questions