Cathy left home at 11.20 a.m. and drove towards the seaside resort. 2 hours later, her cousin left their home and drove towards the same seaside resort at 79 km/h. When the cousin reached the seaside resort at 6.20 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 cousin started driving = 1.20 p.m.
Duration that Cathy's cousin drove from 1.20 p.m. to 6.20 p.m. = 5 h

Distance that Cathy's cousin travelled
= 5 x 79
= 395 km

Distance that Cathy travelled by the time her cousin reached the city
= 395 - 3
= 392 km

Time that Cathy took to travel 392 km = 7 h

Cathy's average speed
= 392 ÷ 7
= 56 km/h

Answer(s): 56 km/h