Tiffany left home at 10.35 a.m. and drove towards the seaside resort. 3 hours later, her grandmother left their home and drove towards the same seaside resort at 94 km/h. When the grandmother reached the seaside resort at 6.35 p.m., Tiffany had another 6 km to travel. What was Tiffany’s average speed? Express your answer in mixed number.
Time that the Tiffany's grandmother started driving = 1.35 p.m.
Duration that Tiffany's grandmother drove from 1.35 p.m. to 6.35 p.m. = 5 h

Distance that Tiffany's grandmother travelled
= 5 x 94
= 470 km

Distance that Tiffany travelled by the time her grandmother reached the city
= 470 - 6
= 464 km

Time that Tiffany took to travel 464 km = 8 h

Tiffany's average speed
= 464 ÷ 8
= 58 km/h

Answer(s): 58 km/h