Opal left home at 10.55 a.m. and drove towards the countryside. 3 hours later, her older sister left their home and drove towards the same countryside at 98 km/h. When the older sister reached the countryside at 6.55 p.m., Opal had another 2 km to travel. What was Opal’s average speed? Express your answer in mixed number.
Time that the Opal's older sister started driving = 1.55 p.m.
Duration that Opal's older sister drove from 1.55 p.m. to 6.55 p.m. = 5 h

Distance that Opal's older sister travelled
= 5 x 98
= 490 km

Distance that Opal travelled by the time her older sister reached the city
= 490 - 2
= 488 km

Time that Opal took to travel 488 km = 8 h

Opal's average speed
= 488 ÷ 8
= 61 km/h

Answer(s): 61 km/h