Question 690704
Average speed is always ( total distance traveled ) / ( time to travel that distance )
{{{ d[1] = m }}}
{{{ d[2] = 3m }}}
{{{ 52 = ( m + 3m ) / ( 8 + 11 ) }}}
{{{ 52 = 4m / 19 }}}
{{{ 4m = 52*19 }}}
{{{ 4m = 988 }}}
{{{ m = 247 }}}
She rode 247 miles on Monday
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Note that the average speed for the 2 days 
is NOT the average of the speeds for each day
For monday:
speed = {{{ m/8 }}}
For tuesday:
speed = {{{ 3m/11 }}}
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The average of these  2 speeds is
{{{ (  m/8  + ( 3m)/11)  / 2 }}}
{{{ m/16 + (3m)/22 = 52 }}}
Multiply both sides by {{{ 16*22 }}}
{{{ 22m + 48m = 52*16*22 }}}
{{{ 70m = 18304 }}}
{{{ m = 261.49 }}}
You get a different answer which is the wrong answer