Question 535406
Add their rates of painting
( 1 room / 6 hrs ) + ( 1 room / 5 hrs ) + ( 1 room / 4 hrs ) = 1 room / x hrs
{{{ 1/6 + 1/5 + 1/4 = 1/x }}}
Multiply both sides by {{{60x}}}
{{{ 10x + 12x + 15x = 60 }}}
{{{ 37x = 60 }}}
{{{ x = 60/37 }}}
{{{ x = 1.622 }}} hrs
{{{ .622*60 = 37.3 }}}
It will take them 1 hr and 37 min
check:
{{{ 1/6 + 1/5 + 1/4 = 1/x }}}
{{{ .1666 + .2 + .25 = .6166 }}}
{{{ .6166 = .6166 }}}
OK