Opal left home at 11.45 a.m. and drove towards the campsite. 3 hours later, her grandfather left their home and drove towards the same campsite at 96 km/h. When the grandfather reached the campsite at 6.45 p.m., Opal had another 6 km to travel. What was Opal’s average speed? Express your answer in mixed number.
Time that the Opal's grandfather started driving = 2.45 p.m.
Duration that Opal's grandfather drove from 2.45 p.m. to 6.45 p.m. = 4 h

Distance that Opal's grandfather travelled
= 4 x 96
= 384 km

Distance that Opal travelled by the time her grandfather reached the city
= 384 - 6
= 378 km

Time that Opal took to travel 378 km = 7 h

Opal's average speed
= 378 ÷ 7
= 54 km/h

Answer(s): 54 km/h