Question 442694
Add their rates of shoveling
Mary's rate: {{{ 1/40 }}}
Bill's rate: {{{ 1/65 }}}
Let {{{t}}} = their time working together
{{{ 1/40 + 1/65 = 1/t }}}
Multiply both sides by LCD {{{ 520t }}}
{{{ 13t + 8t = 520 }}}
{{{ 21t = 520 }}}
{{{ t = 24.76 }}}
They will take 24.76 minutes working together