Esther left home at 11.15 a.m. and drove towards the province. 2 hours later, her mother left their home and drove towards the same province at 91 km/h. When the mother reached the province at 4.15 p.m., Esther had another 6 km to travel. What was Esther’s average speed? Express your answer in mixed number.
Time that the Esther's mother started driving = 1.15 p.m.
Duration that Esther's mother drove from 1.15 p.m. to 4.15 p.m. = 3 h

Distance that Esther's mother travelled
= 3 x 91
= 273 km

Distance that Esther travelled by the time her mother reached the city
= 273 - 6
= 267 km

Time that Esther took to travel 267 km = 5 h

Esther's average speed
= 267 ÷ 5
= 53²₅ km/h

Answer(s): 53²₅ km/h