Question 636514
1. find the rate in which the cans can be filled by each pipe

2. write the equation
Rate of pipe A + Rate of pipe B + Rate of Pipe C = 1 Full Can
Rate of pipe A: 1/20 per min
Rate of pipe B: 1/30 per min
Rate of pipe C: 1/40 per min
{{{x/20+x/30+x/40=1}}}
x= number of min

3. Clear Fractions (*40)
{{{2x+(4/3)x+x=40}}}
{{{13/3x=40}}}
{{{x=40/(13/3)}}}
{{{x=9.23}}}

4. It will take 9 mins and 14 sec. to fill the empty can with all three pipes.