Question 696478
My rate is ( 1 wall ) / ( 10 hrs )
Together our rate is ( 1 wall ) / ( 2 hrs )
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Let your rate  = ( 1 wall ) / ( t hrs )
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Add our rates to get our rate working together
{{{ 1/10 + 1/t = 1/2 }}}
Multiply both sides by {{{ 10t }}}
{{{ t + 10 = 5t }}}
{{{ 4t = 10 }}}
{{{ t = 2.5 }}}
and
{{{ 10 - 2.5 = 7.5 }}}
You can paint the wall in 7.5 hrs less time 
than I can