Betty left home at 10.35 a.m. and drove towards the town. 3 hours later, her auntie left their home and drove towards the same town at 99 km/h. When the auntie reached the town at 6.35 p.m., Betty had another 3 km to travel. What was Betty’s average speed? Express your answer in mixed number.
Time that the Betty's auntie started driving = 1.35 p.m.
Duration that Betty's auntie drove from 1.35 p.m. to 6.35 p.m. = 5 h

Distance that Betty's auntie travelled
= 5 x 99
= 495 km

Distance that Betty travelled by the time her auntie reached the city
= 495 - 3
= 492 km

Time that Betty took to travel 492 km = 8 h

Betty's average speed
= 492 ÷ 8
= 61¹₂ km/h

Answer(s): 61¹₂ km/h