Question 770103
Add their rates of filling
1st pipe's rate:
( 1 tub ) / ( 12 min )
2nd pipe's rate:
( 1 tub ) / ( 8 min )
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Let {{{ t }}} = time in minutes for
both pipes to fill tub
{{{ 1/12 + 1/8 = 1/t }}}
Multiply both sides by {{{ 24t }}}
{{{ 2t + 3t = 24 }}}
{{{ 5t = 24 }}}
{{{ t = 4.8 }}}
It will take them 4.8 min