Question 615249
Let {{{ t }}} = the time in minutes for the 2nd pipeline
to fill the tank
Add their rates of filling to get their rate working together
{{{ 1/45 + 1/t = 1/30 }}}
Multiply both sides by {{{ 90t }}}
{{{ 2t + 90 = 3t }}}
{{{ t = 90 }}}
The 2nd pipeline takes 90 minutes to fill the tank