Dana left home at 11.45 a.m. and drove towards the city. 2 hours later, her younger sister left their home and drove towards the same city at 93 km/h. When the younger sister reached the city at 4.45 p.m., Dana had another 4 km to travel. What was Dana’s average speed? Express your answer in mixed number.
Time that the Dana's younger sister started driving = 1.45 p.m.
Duration that Dana's younger sister drove from 1.45 p.m. to 4.45 p.m. = 3 h

Distance that Dana's younger sister travelled
= 3 x 93
= 279 km

Distance that Dana travelled by the time her younger sister reached the city
= 279 - 4
= 275 km

Time that Dana took to travel 275 km = 5 h

Dana's average speed
= 275 ÷ 5
= 55 km/h

Answer(s): 55 km/h