Question 1017683
Find the ratio of the areas of the 2 rooms
1st room:
{{{ A[1] = 4*12*10 }}}
{{{ A[1] = 480 }}} ft2
2nd room:
{{{ A[2] = 4*25*12 }}}
{{{ A[2] = 1200 }}}
{{{ A[2] / A[1] = 2.5/1 }}}
{{{ A[2] / A[1] = 5/2 }}}
--------------------
Each member of Jo's crew works
at the rate {{{ 2/t[1] }}} where {{{ 2 }}}
is from the above ratio, and {{{ t }}}
is time in hrs to do the work
[ 3 members ] / [ 4 hrs ] = [ 2 units of work ] / [ t[1] hrs ] 
{{{ 3/4 = 2/t[1] }}}
{{{ 3t[1] = 8 }}}
{{{ t[1] = 8/3 }}} hrs
----------------
For the crew of 5:
[ 5 members ] / [ time for them to finish ] = [ units of work ] / [ time for 1 member ]
{{{ 5/t[2] = 5/( 8/3) }}}
{{{ 1/t[2] = 1/(8/3) }}}
{{{ t[2] = 8/3 }}}
-------------
I get each crew takes the same time to paint their rooms:
{{{ 8/3 = 2 + 2/3 }}}
2 hrs 40 min
--------------
Hope I got it! Definitely get another opinion
on this -my logic could have gotten twisted.