Question

Paul, Brendan, and Charlie are chopping wood. It would take Paul 10 hours to chop up one cord of firewood. It would take Brendan 12 hours to chop one cord, and it would take Charlie 15 hours to do the same job by himself. How long will it take the three of them working together?
It will take blank hours for the three boys to chop up one cord of firewood.

The solution is

Answer 1

Answer: It will take the 4 hours