Usha left home at 11.45 a.m. and drove towards the suburb. 3 hours later, her cousin left their home and drove towards the same suburb at 86 km/h. When the cousin reached the suburb at 7.45 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 cousin started driving = 2.45 p.m.
Duration that Usha's cousin drove from 2.45 p.m. to 7.45 p.m. = 5 h

Distance that Usha's cousin travelled
= 5 x 86
= 430 km

Distance that Usha travelled by the time her cousin reached the city
= 430 - 6
= 424 km

Time that Usha took to travel 424 km = 8 h

Usha's average speed
= 424 ÷ 8
= 53 km/h

Answer(s): 53 km/h