Question 513272
Average speed is ( total distance ) / ( total time )
During the 1st 3 hrs:
{{{ d = 10*3 }}}
{{{ d = 30 }}} mi
During the last hour:
{{{ d = 20*1 }}}
{{{ d = 20 }}} mi
Average speed =
{{{ ( 30 + 20 ) / ( 3 + 1 + 1 ) }}}
{{{ 50 / 5 = 10 }}}
10 mi/hr