Irene left home at 10.35 a.m. and drove towards the seaside resort. 3 hours later, her mother left their home and drove towards the same seaside resort at 85 km/h. When the mother reached the seaside resort at 6.35 p.m., Irene had another 3 km to travel. What was Irene’s average speed? Express your answer in mixed number.
Time that the Irene's mother started driving = 1.35 p.m.
Duration that Irene's mother drove from 1.35 p.m. to 6.35 p.m. = 5 h

Distance that Irene's mother travelled
= 5 x 85
= 425 km

Distance that Irene travelled by the time her mother reached the city
= 425 - 3
= 422 km

Time that Irene took to travel 422 km = 8 h

Irene's average speed
= 422 ÷ 8
= 52³₄ km/h

Answer(s): 52³₄ km/h