Jade left home at 11.20 a.m. and drove towards the countryside. 2 hours later, her grandmother left their home and drove towards the same countryside at 90 km/h. When the grandmother reached the countryside at 4.20 p.m., Jade had another 5 km to travel. What was Jade’s average speed? Express your answer in mixed number.
Time that the Jade's grandmother started driving = 1.20 p.m.
Duration that Jade's grandmother drove from 1.20 p.m. to 4.20 p.m. = 3 h

Distance that Jade's grandmother travelled
= 3 x 90
= 270 km

Distance that Jade travelled by the time her grandmother reached the city
= 270 - 5
= 265 km

Time that Jade took to travel 265 km = 5 h

Jade's average speed
= 265 ÷ 5
= 53 km/h

Answer(s): 53 km/h