



 
Hi Ken, The key to this problem is that rate is distance divided by time, in your case kilometers divided by hours. Let the time that the cars is driven on concrete by $t$ hours. Since the total time is 5.5 hours the time that the car is driven on a rough road is $5.5  t$ hours. Use that fact that distance divided by time to write an equation for the distance that the car travels on concrete. Do the same for the distance that the car travels on a rough road. The total distance is 225 km. Solve for $t.$ Penny  


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