# First pipe can fill a tank in 12 Second pipe can fill the same tank in 6 hours

First pipe can fill a tank in 12 Second pipe can fill the same tank in 6 hours. Third pipe in 4 hours. How long will it take to fill the tank if all the 3 pipes are opened simultaneously?

- 2 hrs
- 3 hrs.
- 4 hrs.
- 12 hrs.