Cathy left home at 11.45 a.m. and drove towards the campsite. 3 hours later, her uncle left their home and drove towards the same campsite at 81 km/h. When the uncle reached the campsite at 7.45 p.m., Cathy had another 3 km to travel. What was Cathy’s average speed? Express your answer in mixed number.
Time that the Cathy's uncle started driving = 2.45 p.m.
Duration that Cathy's uncle drove from 2.45 p.m. to 7.45 p.m. = 5 h

Distance that Cathy's uncle travelled
= 5 x 81
= 405 km

Distance that Cathy travelled by the time her uncle reached the city
= 405 - 3
= 402 km

Time that Cathy took to travel 402 km = 8 h

Cathy's average speed
= 402 ÷ 8
= 50¹₄ km/h

Answer(s): 50¹₄ km/h