Shiyun left home at 10.10 a.m. and drove towards the campsite. 3 hours later, her younger brother left their home and drove towards the same campsite at 82 km/h. When the younger brother reached the campsite at 6.10 p.m., Shiyun had another 4 km to travel. What was Shiyun’s average speed? Express your answer in mixed number.
Time that the Shiyun's younger brother started driving = 1.10 p.m.
Duration that Shiyun's younger brother drove from 1.10 p.m. to 6.10 p.m. = 5 h

Distance that Shiyun's younger brother travelled
= 5 x 82
= 410 km

Distance that Shiyun travelled by the time her younger brother reached the city
= 410 - 4
= 406 km

Time that Shiyun took to travel 406 km = 8 h

Shiyun's average speed
= 406 ÷ 8
= 50³₄ km/h

Answer(s): 50³₄ km/h