Math
posted by Fran 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, what is the total distance she walks in km?

if the distance is a hilly km and b flat km, then
a/2 + b/3 + b/3 + a/6 = 6
4a + 4b = 36
a + b = 9
so, she walks 18 km