Erika left home at 11.15 a.m. and drove towards the suburb. 2 hours later, her father left their home and drove towards the same suburb at 97 km/h. When the father reached the suburb at 4.15 p.m., Erika had another 2 km to travel. What was Erika’s average speed? Express your answer in mixed number.
Time that the Erika's father started driving = 1.15 p.m.
Duration that Erika's father drove from 1.15 p.m. to 4.15 p.m. = 3 h

Distance that Erika's father travelled
= 3 x 97
= 291 km

Distance that Erika travelled by the time her father reached the city
= 291 - 2
= 289 km

Time that Erika took to travel 289 km = 5 h

Erika's average speed
= 289 ÷ 5
= 57⁴₅ km/h

Answer(s): 57⁴₅ km/h