



 
Hi Christian, The important fact here is that \[\mbox{ rate} = \frac{\mbox{distance}}{\mbox{time}}\] Suppose that the distance from the start to the fixed point is $d$ miles, the time it takes to travel this distance at 70 mph is $t$ hours, the time it takes to travel this distance at 60 mph is $t_{1}$ hours and the time it takes to travel this distance at 80 mph is $t_{2}$ hours. Use the fact that rate is distance over time to find $t, t_1$ and $t_2$ as functions of $d$ and ask is $2t = t_1 + t_{2}?$ Penny  


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