Posted by Rezu on .
Elizabeth visits her friend Andrew and then returns home by the same route. She always walks 2km/h when going uphill, 6km/h when going downhill and 3km/h when on level ground. If her total walking time is 6 hours, then what is the total distance she walks in km?
She walks 18km in total.

Math (Grade 9) 
Steve,
using u,d,f for uphill, downhill, flat distances on the outward journey,
recall that time = distance/speed
she walks 9 km in each direction
(u/2 + f/3 + d/6) + (d/2 + f/3 + u/6) = 6
2u/3 + 2f/3 + 2d/3 = 6
u + f + d = 9
you are correct. the round trip is 18 km.