Nicole left home at 11.20 a.m. and drove towards the city. 3 hours later, her older sister left their home and drove towards the same city at 87 km/h. When the older sister reached the city at 7.20 p.m., Nicole had another 3 km to travel. What was Nicole’s average speed? Express your answer in mixed number.
Time that the Nicole's older sister started driving = 2.20 p.m.
Duration that Nicole's older sister drove from 2.20 p.m. to 7.20 p.m. = 5 h

Distance that Nicole's older sister travelled
= 5 x 87
= 435 km

Distance that Nicole travelled by the time her older sister reached the city
= 435 - 3
= 432 km

Time that Nicole took to travel 432 km = 8 h

Nicole's average speed
= 432 ÷ 8
= 54 km/h

Answer(s): 54 km/h