Question 908453
A {{{ 6 }}} hr trip at {{{ 45 }}} mi/hr means:
{{{ d[1] = 45*6 }}}
{{{ d[1] = 270 }}} mi
is the distance of the entire trip
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For the 1st hr, 
{{{ d[2] = 25*1 }}}
{{{ d[2] = 25 }}} mi
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{{{ 270 - 25 = 245 }}} mi
is the distance left to travel
after the 1st hr
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Let {{{ s }}} = speed needed to make
the entire trip ion {{{ 6 }}} hrs
There is {{{ 6 - 1 = 5 }}} hrs left
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{{{ 245 = s*5 }}}
{{{ s = 245/5 }}}
{{{ s = 49 }}}
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The average speed should be 49 mi/hr
for the last 5 hrs
to make the trip on time