Sabrina left home at 10.50 a.m. and drove towards the city. 3 hours later, her grandfather left their home and drove towards the same city at 89 km/h. When the grandfather reached the city at 5.50 p.m., Sabrina had another 6 km to travel. What was Sabrina’s average speed? Express your answer in mixed number.
Time that the Sabrina's grandfather started driving = 1.50 p.m.
Duration that Sabrina's grandfather drove from 1.50 p.m. to 5.50 p.m. = 4 h

Distance that Sabrina's grandfather travelled
= 4 x 89
= 356 km

Distance that Sabrina travelled by the time her grandfather reached the city
= 356 - 6
= 350 km

Time that Sabrina took to travel 350 km = 7 h

Sabrina's average speed
= 350 ÷ 7
= 50 km/h

Answer(s): 50 km/h