Ivory left home at 11.20 a.m. and drove towards the campsite. 3 hours later, her younger sister left their home and drove towards the same campsite at 82 km/h. When the younger sister reached the campsite at 7.20 p.m., Ivory had another 2 km to travel. What was Ivory’s average speed? Express your answer in mixed number.
Time that the Ivory's younger sister started driving = 2.20 p.m.
Duration that Ivory's younger sister drove from 2.20 p.m. to 7.20 p.m. = 5 h

Distance that Ivory's younger sister travelled
= 5 x 82
= 410 km

Distance that Ivory travelled by the time her younger sister reached the city
= 410 - 2
= 408 km

Time that Ivory took to travel 408 km = 8 h

Ivory's average speed
= 408 ÷ 8
= 51 km/h

Answer(s): 51 km/h