Maria and Kim left town at 9:00 am and traveled the same route in separate cars. Kim drove 3 h at a steady speed, then slowed down 15km/h for 3 more hours. Maria averaged 5 km/h more than Kim's original speed for the entire trip and arrived at their destination at 2 pm. What was Kim's original speed?

70 km/h

Step-by-step explanation:

Let the original speed of Kim = x km/h

Kim drove with this speed for 3 hours.

Total distance covered by Kim during this period is 3 * x km

After 3 hours, Kim slowed down by 15 km/h.

So, new speed of Kim is (x-15) km/h

Kim drove at this speed for another 3 hours.

Distance covered by Kim during this period = 3 * (x-15) km

So, total distance covered by Kim is / [3x + (3x-45) / ] km

This is equivalent to / [6x - 45/] km

Maria's speed = (x+5) km/h

Maria started at 9 am and reached the destination at 2 pm. So she drove for 5 hours.

Total distance covered by Maria is / [5 * (x+5) / ] km

This is equivalent to / [5x + 25/] km

As per the given data, 6x - 45 = 5x + 25

=> 6x - 5x = 45 + 25

=> x = 70

So Kim's original speed was 70 km/h