Question 1120554
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The time equation is 


{{{12/x}}} + {{{12/50}}} = {{{24/60}}}.


Solve for x, where x is the speed on the second lap.


12*50*60 + 12*60*x = 24*50*x


12*50*60  = 24*50*x - 12*60*x


x = {{{(12*50*60)/(24*50-12*60)}}} = 75.


<U>Answer</U>.  The speed under the question is 75 mph.


<U>Check</U>.  {{{12/50}}} + {{{12/75}}} = {{{12*(1/50 + 1/75)}}} = {{{12*(6/300 + 4/300)}}} = {{{12*(10/300)}}} = {{{12*1/30}}} = {{{24/60}}} of an hour = 24 minutes.


        ! Correct !
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