Question 544460
the new one's rate of paving is {{{ 1/8 }}} km/hr
The old machine's rate is {{{ 1/12 }}} km/hr
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Add their rate off paving to get their rate of
paving together, {{{ 20/t }}}, where {{{t}}} is
their time  in hours to pave {{{20}}} km
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{{{ 1/8 + 1/12 = 20/t }}}
Multiply both sides by {{{ 24t }}}
{{{ 3t + 2t = 20*24 }}}
{{{ 5t = 480 }}}
{{{ t = 96 }}}
It will take them 96 hrs