Nora left home at 11.10 a.m. and drove towards the suburb. 2 hours later, her younger sister left their home and drove towards the same suburb at 91 km/h. When the younger sister reached the suburb at 4.10 p.m., Nora had another 2 km to travel. What was Nora’s average speed? Express your answer in mixed number.
Time that the Nora's younger sister started driving = 1.10 p.m.
Duration that Nora's younger sister drove from 1.10 p.m. to 4.10 p.m. = 3 h

Distance that Nora's younger sister travelled
= 3 x 91
= 273 km

Distance that Nora travelled by the time her younger sister reached the city
= 273 - 2
= 271 km

Time that Nora took to travel 271 km = 5 h

Nora's average speed
= 271 ÷ 5
= 54¹₅ km/h

Answer(s): 54¹₅ km/h