Question 955543
Let x= amount of time needed to fill tank if they work together
Together the three men fill at the rate of 1/x of the tank per min

man1 fills at the rate of 1/60 of a tank per min
man2 fills at the rate of 1/30 of a tank per min
man3 fills at the rate of 1/20 of a tank per min
sooooo
1/60 + 1/30 + 1/20= 1/x. multiply each term by 60x
x+2x+3x=60
6x=60
x=10 min---time needed if they work together
CK
In 10 min, man1 fills 10/60=1/6 of the tank
In 10min, man2 fills 10/30=1/3 of the tank
In 10 min, man3 fills 10/20=1/2 of the tank
Now 1/6 +1/3+1/2 should add up to one tank and they do:)
Hope this helps---ptaylor