Rachel left home at 11.20 a.m. and drove towards the campsite. 2 hours later, her mother left their home and drove towards the same campsite at 100 km/h. When the mother reached the campsite at 4.20 p.m., Rachel had another 4 km to travel. What was Rachel’s average speed? Express your answer in mixed number.
Time that the Rachel's mother started driving = 1.20 p.m.
Duration that Rachel's mother drove from 1.20 p.m. to 4.20 p.m. = 3 h

Distance that Rachel's mother travelled
= 3 x 100
= 300 km

Distance that Rachel travelled by the time her mother reached the city
= 300 - 4
= 296 km

Time that Rachel took to travel 296 km = 5 h

Rachel's average speed
= 296 ÷ 5
= 59¹₅ km/h

Answer(s): 59¹₅ km/h