Roshel left home at 11.55 a.m. and drove towards the countryside. 2 hours later, her grandfather left their home and drove towards the same countryside at 88 km/h. When the grandfather reached the countryside at 5.55 p.m., Roshel had another 4 km to travel. What was Roshel’s average speed? Express your answer in mixed number.
Time that the Roshel's grandfather started driving = 1.55 p.m.
Duration that Roshel's grandfather drove from 1.55 p.m. to 5.55 p.m. = 4 h

Distance that Roshel's grandfather travelled
= 4 x 88
= 352 km

Distance that Roshel travelled by the time her grandfather reached the city
= 352 - 4
= 348 km

Time that Roshel took to travel 348 km = 6 h

Roshel's average speed
= 348 ÷ 6
= 58 km/h

Answer(s): 58 km/h