Question 769300
Add their rates of cleaning to get
their rate working together
Nancy's rate:
( 1 office cleaned ) / ( t minutes )
Amy's rate:
( 1 office cleaned ) / ( 2t minutes )
Working together:
( 1 ofice cleaned ) / ( 30 minutes )
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{{{ 1/t + 1/( 2t ) = 1/30 }}}
Multiply both sides by {{{ 30t }}}
{{{ 30 + 15 = t }}}
{{{ t = 45 }}}
and
{{{ 2t = 90 }}}
Nancy takes 45 min
Amy takes 90 min