Math (Grade 9)
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.

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.