Usha left home at 11.30 a.m. and drove towards the seaside resort. 3 hours later, her uncle left their home and drove towards the same seaside resort at 81 km/h. When the uncle reached the seaside resort at 7.30 p.m., Usha had another 5 km to travel. What was Usha’s average speed? Express your answer in mixed number.
Time that the Usha's uncle started driving = 2.30 p.m.
Duration that Usha's uncle drove from 2.30 p.m. to 7.30 p.m. = 5 h

Distance that Usha's uncle travelled
= 5 x 81
= 405 km

Distance that Usha travelled by the time her uncle reached the city
= 405 - 5
= 400 km

Time that Usha took to travel 400 km = 8 h

Usha's average speed
= 400 ÷ 8
= 50 km/h

Answer(s): 50 km/h