Question 680819
Add their rates of filling ( or emptying )
to get their rate when used together
( 1 pool filled / 2 hrs ) + ( 1 pool filled / 5 hrs ) + (1 pool ( filled or emptied )
= ( 1 pool filled / t hrs )
{{{ 1/2 + 1/5 + 1/9 = 1/t }}}
Multiply both sides by {{{ 90t }}}
{{{ 45t + 18t + 10t = 90 }}}
{{{ 73t = 90 }}}
{{{ t = 1.233 }}} hrs
{{{ .233*60 = 14 }}}
It will take 1 hr and 14 min
check:
{{{ .5 + .2 + .111 = 1/t }}}
{{{ .8111 = 1/t }}}
{{{ t = 1.233 }}}
OK