Natalie left home at 10.55 a.m. and drove towards the campsite. 3 hours later, her auntie left their home and drove towards the same campsite at 90 km/h. When the auntie reached the campsite at 6.55 p.m., Natalie had another 4 km to travel. What was Natalie’s average speed? Express your answer in mixed number.
Time that the Natalie's auntie started driving = 1.55 p.m.
Duration that Natalie's auntie drove from 1.55 p.m. to 6.55 p.m. = 5 h

Distance that Natalie's auntie travelled
= 5 x 90
= 450 km

Distance that Natalie travelled by the time her auntie reached the city
= 450 - 4
= 446 km

Time that Natalie took to travel 446 km = 8 h

Natalie's average speed
= 446 ÷ 8
= 55³₄ km/h

Answer(s): 55³₄ km/h