Question 955543
Man1 fills 1 tank/60 minutes=1/60 tank per minute. We will convert the other fractions to this denominator to add.
Man2 fills 1 tank/30 minutes=1/30 tank per minute.1/30 tank/minute(2/2)=2/60 tank/minute.
Man3 fills 1 tank/20 minutes=1/20 tank per minute.1/20 tank/minute(3/3)=3/60 tank/minute.
Together:
Man1+Man2+Man3=1/60 tank/minute+2/60 tank/minute+3/60 tank /minute=6/60 tank/minute=1/10 tank/minute.
To fill 1 tank at 1/10 tank/minute=(1tank)/(1/10tank/min)=10 minutes
The three together can fill the tank in ten minutes.