Question 855813
Mr Bean's rate:
( 1 car ) / ( 15 min )
Son's rate:
( 1 car ) / ( 30 min )
Working together:
( 1 car ) / ( t min )
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Add their rates of working
{{{ 1/15 + 1/30 = 1/t }}}
Multiply both sides by {{{ 30t }}}
{{{ 2t + t = 30 }}}
{{{ 3t = 30 }}}
{{{ t = 10 }}}
Working together, it takes them
10 min to wash a car