Question 14
After Nadia goes up a hill, she finds a level path on top of length 2.5 km. At the end of it, she goes down the hill to a pond. Later, she goes back along the same route. Her walking speed is 5 kph, but it decreases to 4 kph going up the hill, and increases to 6 kph going down the hill. Her outward journey takes 1 hour 36 minutes but her return journey takes 1 hour 39 minutes. She does not stop anywhere at any time. What is the length, in km, from start point to the pond?