Question 682497
Add the rate of filling and subtract the rate of draining
Rate of filling = ( 1 pool filled ) / ( 15 min to fill )
Rate of draining = ( 1 pool drained ) / ( 20 min to drain )
Let {{{ t }}} = time in minutes to fill the pool
{{{ 1/15 - 1/20 = 1/t }}}
Multiply both sides by
{{{ 60t }}}
{{{ 4t - 3t = 60 }}}
{{{ t = 60 }}}
It takes 1 hour to fill the pool with drain open
I think you are right, as long as the data is right.