Nora left home at 10.30 a.m. and drove towards the seaside resort. 3 hours later, her younger sister left their home and drove towards the same seaside resort at 99 km/h. When the younger sister reached the seaside resort at 6.30 p.m., Nora had another 5 km to travel. What was Nora’s average speed? Express your answer in mixed number.
Time that the Nora's younger sister started driving = 1.30 p.m.
Duration that Nora's younger sister drove from 1.30 p.m. to 6.30 p.m. = 5 h

Distance that Nora's younger sister travelled
= 5 x 99
= 495 km

Distance that Nora travelled by the time her younger sister reached the city
= 495 - 5
= 490 km

Time that Nora took to travel 490 km = 8 h

Nora's average speed
= 490 ÷ 8
= 61¹₄ km/h

Answer(s): 61¹₄ km/h