Diana left home at 11.55 a.m. and drove towards the city. 2 hours later, her younger brother left their home and drove towards the same city at 93 km/h. When the younger brother reached the city at 4.55 p.m., Diana had another 5 km to travel. What was Diana’s average speed? Express your answer in mixed number.
Time that the Diana's younger brother started driving = 1.55 p.m.
Duration that Diana's younger brother drove from 1.55 p.m. to 4.55 p.m. = 3 h

Distance that Diana's younger brother travelled
= 3 x 93
= 279 km

Distance that Diana travelled by the time her younger brother reached the city
= 279 - 5
= 274 km

Time that Diana took to travel 274 km = 5 h

Diana's average speed
= 274 ÷ 5
= 54⁴₅ km/h

Answer(s): 54⁴₅ km/h