Question 1014218
Convert minutes to hrs
{{{ 40/60 = 2/3 }}} hrs
The one-way distance is:
{{{ d = 30*(2/3) = 20 }}} km
and, for the return to start:
{{{ 20 = 20*t }}}
{{{ t = 1 }}} hr
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Average speed is always
[ total distance ] / [ total time ]
{{{ ( 20 + 20 ) / ( 2/3 + 1 ) }}}
{{{ 40/( 5/3 ) }}}
{{{ (3/5)*40 = 24 }}}
The average speed is 24 km/hr