Question 458152
Add the rates of flow of both pipes
{{{ 1/18 + 1/24 = 1/x }}}
This is read as:
(1 tankful)/(A's time to fill it) + ( 1 tankful)/(B's time to fill it) = (1 tankful)/(A and B's time to fill it)
Multiply both sides by {{{ 72x }}}
{{{ 4x + 3x = 72 }}}
{{{ 7x = 72 }}}
{{{  x = 10.286 }}}
{{{ .286*60 = 17.143 }}}
{{{ .143*60 = 8.57 }}}
It takes both pipes 10 hrs 17 min 9 sec
check:
{{{ 1/18 + 1/24 = 1/10.286 }}}
{{{ .0556 + .04167 = .0972 }}}
{{{ .0973 = .0972 }}}
close enough