Question 817842
  <pre><font face = "Tohoma" size = 3 color = "indigo"><b> 
Hi,
one pump fills a tank 2 times as fast as another pump.
Let x and {{{green(2x)}}} represent  their rates
If the pumps work together they fill the tank in 8 minutes. 
{{{1/x + 1/(2x) = 1/(8min)}}}   |Multiplying thru by 8x so as all denominators = 1
   8 + 4 = x
    12min = x, the other pump takes 24min   {{{green(2x)}}}