Penelope left home at 11.50 a.m. and drove towards the suburb. 2 hours later, her cousin left their home and drove towards the same suburb at 85 km/h. When the cousin reached the suburb at 4.50 p.m., Penelope had another 4 km to travel. What was Penelope’s average speed? Express your answer in mixed number.
Time that the Penelope's cousin started driving = 1.50 p.m.
Duration that Penelope's cousin drove from 1.50 p.m. to 4.50 p.m. = 3 h

Distance that Penelope's cousin travelled
= 3 x 85
= 255 km

Distance that Penelope travelled by the time her cousin reached the city
= 255 - 4
= 251 km

Time that Penelope took to travel 251 km = 5 h

Penelope's average speed
= 251 ÷ 5
= 50¹₅ km/h

Answer(s): 50¹₅ km/h