Sabrina left home at 11.45 a.m. and drove towards the seaside resort. 2 hours later, her younger brother left their home and drove towards the same seaside resort at 90 km/h. When the younger brother reached the seaside resort at 4.45 p.m., Sabrina had another 2 km to travel. What was Sabrina’s average speed? Express your answer in mixed number.
Time that the Sabrina's younger brother started driving = 1.45 p.m.
Duration that Sabrina's younger brother drove from 1.45 p.m. to 4.45 p.m. = 3 h

Distance that Sabrina's younger brother travelled
= 3 x 90
= 270 km

Distance that Sabrina travelled by the time her younger brother reached the city
= 270 - 2
= 268 km

Time that Sabrina took to travel 268 km = 5 h

Sabrina's average speed
= 268 ÷ 5
= 53³₅ km/h

Answer(s): 53³₅ km/h