Natalie left home at 11.25 a.m. and drove towards the city. 2 hours later, her younger brother left their home and drove towards the same city at 85 km/h. When the younger brother reached the city at 6.25 p.m., Natalie had another 5 km to travel. What was Natalie’s average speed? Express your answer in mixed number.
Time that the Natalie's younger brother started driving = 1.25 p.m.
Duration that Natalie's younger brother drove from 1.25 p.m. to 6.25 p.m. = 5 h

Distance that Natalie's younger brother travelled
= 5 x 85
= 425 km

Distance that Natalie travelled by the time her younger brother reached the city
= 425 - 5
= 420 km

Time that Natalie took to travel 420 km = 7 h

Natalie's average speed
= 420 ÷ 7
= 60 km/h

Answer(s): 60 km/h