Sabrina left home at 11.25 a.m. and drove towards the suburb. 2 hours later, her auntie left their home and drove towards the same suburb at 91 km/h. When the auntie reached the suburb at 4.25 p.m., Sabrina had another 3 km to travel. What was Sabrina’s average speed? Express your answer in mixed number.
Time that the Sabrina's auntie started driving = 1.25 p.m.
Duration that Sabrina's auntie drove from 1.25 p.m. to 4.25 p.m. = 3 h

Distance that Sabrina's auntie travelled
= 3 x 91
= 273 km

Distance that Sabrina travelled by the time her auntie reached the city
= 273 - 3
= 270 km

Time that Sabrina took to travel 270 km = 5 h

Sabrina's average speed
= 270 ÷ 5
= 54 km/h

Answer(s): 54 km/h