A cistern can be filled by one tap in 8 hours, and by another in 4 hours. How long will it take to fill the cistern if both taps are opened together?

A cistern can be filled by one tap in 4 hours and by another in 3 hours. How long will it take to fill it if both taps are opened together ?

A cistern can be filled by a tap in 6 hours and emptied by an outlet pipe in 8 hours. How long will it take to fill the cistern if both the tap and the pipe are opened together ?

A cistern can be filled by a tap in 6 hours and emptied by an outlet pipe in 8 hours. How long will it take to fill the cistern if both the tap and the pipe are opened together ?

10 boys can dig a pitch in 12 hours. How long will 8 boys take to do it?

Anil can do a piece of work in 5 days and ankur in 4 days. How long will they take to do the same work, if they work together?

Sita can finish typing a 100 page document in 9 hours, Mita in 6 hours and Rita in 12 hours. How long will they take to type a 100 page document if they work together?

A car travels 165 km in 3 hours. How long will it take to travel 440 km?

Because of anticipated heavy rain , the water level in a swimming pool must be lowered by 1 foot . Opening drain A lowers the level by 1 foot in 4 hours , whereas opening the smaller drain B does the job in 6 hours . How long will it take to lower the water level by 1 foot if both drains are opended ? An equation that solves the problem is

If 6 oil tankers can be filled by a pipe in 4 1/2 hours, how long does the pipe take to fill 4 such oil tankers?

12 pipes, all of the same size, fill a tank in 42 minutes. How long will it take to fill the same tank,if 21 pipes of the same size are used ?