Usha left home at 11.25 a.m. and drove towards the province. 2 hours later, her grandmother left their home and drove towards the same province at 92 km/h. When the grandmother reached the province at 4.25 p.m., Usha had another 6 km to travel. What was Usha’s average speed? Express your answer in mixed number.
Time that the Usha's grandmother started driving = 1.25 p.m.
Duration that Usha's grandmother drove from 1.25 p.m. to 4.25 p.m. = 3 h

Distance that Usha's grandmother travelled
= 3 x 92
= 276 km

Distance that Usha travelled by the time her grandmother reached the city
= 276 - 6
= 270 km

Time that Usha took to travel 270 km = 5 h

Usha's average speed
= 270 ÷ 5
= 54 km/h

Answer(s): 54 km/h