There are three pipes to the dolphinarium. With the help of the first one can fill the dolphinarium in 8 hours

There are three pipes to the dolphinarium. With the help of the first one can fill the dolphinarium in 8 hours, with the help of the second in 6 hours, and with the help of the third in 4 hours. What part of the dolphinarium will be filled in 1 hour if three pipes are open?

The first pipe will fill 1/8 part of the dolphinarium in an hour, the second – 1/6 part, the third – 1/4 part.
If you open three pipes, then the following part of the dolphinarium will be filled in an hour:
1/8 + 1/6 + 1/4 = 3/24 + 4/24 + 6/24 = 13/24;
Answer: In an hour, three pipes will fill the 13/24 part of the dolphinarium.