Wendy left home at 11.35 a.m. and drove towards the countryside. 2 hours later, her younger sister left their home and drove towards the same countryside at 97 km/h. When the younger sister reached the countryside at 4.35 p.m., Wendy had another 6 km to travel. What was Wendy’s average speed? Express your answer in mixed number.
Time that the Wendy's younger sister started driving = 1.35 p.m.
Duration that Wendy's younger sister drove from 1.35 p.m. to 4.35 p.m. = 3 h

Distance that Wendy's younger sister travelled
= 3 x 97
= 291 km

Distance that Wendy travelled by the time her younger sister reached the city
= 291 - 6
= 285 km

Time that Wendy took to travel 285 km = 5 h

Wendy's average speed
= 285 ÷ 5
= 57 km/h

Answer(s): 57 km/h