Question 560083
The average speed is always ( total distance traveled ) / ( total elapsed time )
At 60 mi/hr:
{{{ d = 60*40 }}}
{{{ d = 2400 }}} mi
At 75 mi/hr:
{{{ d = 75*2 }}}
{{{ d = 150 }}} mi
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Total distance = {{{ 2400 + 150 }}}
{{{ 2400 + 150 = 2550 }}} mi
Total time is {{{ 40 + 2 = 42 }}} hrs
Total distance /total time is {{{ 2550/42 = 60.714 }}} mi/hr