Mary left home at 11.15 a.m. and drove towards the countryside. 2 hours later, her mother left their home and drove towards the same countryside at 89 km/h. When the mother reached the countryside at 5.15 p.m., Mary had another 2 km to travel. What was Mary’s average speed? Express your answer in mixed number.
Time that the Mary's mother started driving = 1.15 p.m.
Duration that Mary's mother drove from 1.15 p.m. to 5.15 p.m. = 4 h

Distance that Mary's mother travelled
= 4 x 89
= 356 km

Distance that Mary travelled by the time her mother reached the city
= 356 - 2
= 354 km

Time that Mary took to travel 354 km = 6 h

Mary's average speed
= 354 ÷ 6
= 59 km/h

Answer(s): 59 km/h