Question 22995
If Sally can paint the house in 4 hours, then in 1 hour she can paint 1/4 of the house.

If John can paint the house in 6 hours, then in 1 hour he can paint 1/6 of the house.

Let x = number of hours it would take them together to paint the house, then working together, in 1 hour they can paint 1/x of the house. 


The equation is this:

{{{1/4 + 1/6 = 1/x}}}


Multiply both sides by the LCD which is 12x:
{{{(12x)* (1/4) + (12x)*(1/6) = (12x)*(1/x) }}}

{{{3x + 2x = 12}}}
{{{5x = 12}}}
{{{x = 12/5}}} = 2.4 hours


R^2 at SCC