Question 959645
Add their rates of filling
Let {{{ t }}} = time in minutes to fill
sink with just hot water faucet open
---------------------------------
{{{ 1/5 + 1/t = 1/4 }}}
Multiply both sides by {{{ 20t }}}
{{{ 4t + 20 = 5t }}}
{{{ t = 20 }}}
With just the hot water faucet open,
the sink fills in 20 min
---------------------
check:
{{{ 1/5 + 1/t = 1/4 }}}
{{{ 1/5 + 1/20 = 1/4 }}}
{{{ 4/20 + 1/20 = 5/20 }}}
{{{ 5/20 = 5/20 }}}
OK