Mrs Chen left home at 8 a.m. and drove towards the city. 1¹₃ hour later, Mr Chen left the house and drove at an average speed of 82 km/h towards the city. When Mr Chen reached his destination at 1 p.m., Mrs Chen was 19 km away from the city. Find Mrs Chen’s average speed in km/h. Express your answer in mixed number.
1 h = 60 min 
¹₃ h = ¹₃ x 60 = 20 min
1¹₃ = 1 h 20 min

1 h 20 min after 8 a.m. = 9.20 a.m.

Time that Mr Chen left the house = 9.20 a.m.

Time that Mr Chen took from 9.20 a.m. to 1 p.m. to reach his destination = 3 h 40 min

1 min = ¹₆₀ h
40 min = ⁴⁰₆₀ h = ²₃ h
3 h 40 min = 3²₃ h

Distance that Mr Chen drove
= 3²₃ x 82
= 300²₃ km

Distance that Mrs Chen drove when Mr Chen reached
= 300²₃ - 19 
= 281²₃ km

Time that Mrs Chen took to travel from 8 a.m. to 1 p.m. = 5 h

Mrs Chen's average speed
= 281²₃ ÷ 5
= 56¹₃ km/h

Answer(s): 56¹₃ km/h