Barbara left home at 11.55 a.m. and drove towards the province. 2 hours later, her older sister left their home and drove towards the same province at 92 km/h. When the older sister reached the province at 4.55 p.m., Barbara had another 4 km to travel. What was Barbara’s average speed? Express your answer in mixed number.
Time that the Barbara's older sister started driving = 1.55 p.m.
Duration that Barbara's older sister drove from 1.55 p.m. to 4.55 p.m. = 3 h

Distance that Barbara's older sister travelled
= 3 x 92
= 276 km

Distance that Barbara travelled by the time her older sister reached the city
= 276 - 4
= 272 km

Time that Barbara took to travel 272 km = 5 h

Barbara's average speed
= 272 ÷ 5
= 54²₅ km/h

Answer(s): 54²₅ km/h