Question 854115
The rate of filling of the 1st pipe is:
( 1 pool filled ) / ( 20 hrs )
The rate of filling of the 2nd pipe is:
( 1 pool filled ) / ( 60 hrs )
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Let {{{ t }}} = the time in hours for the pipes
to fill the pool together. the rate of both filling is:
( 1 pool filled ) / ( t hrs )
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To get the rate of filling of both pipes
together, add their rates of filling:
{{{ 1/20 + 1/60 = 1/t }}}
Multiply both sides by {{{ 60t }}}
{{{ 3t + t = 60 }}}
{{{ 4t = 60 }}}
{{{ t = 15 }}}
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With both pipes filling together, the
pool is filled in 15 hrs