Mrs Lim left home at 8 a.m. and drove towards the city. 2²₃ hour later, Mr Lim left the house and drove at an average speed of 104 km/h towards the city. When Mr Lim reached his destination at 3 p.m., Mrs Lim was 22 km away from the city. Find Mrs Lim’s average speed in km/h. Express your answer in mixed number.
1 h = 60 min 
²₃ h = ²₃ x 60 = 40 min
2²₃ = 2 h 40 min

2 h 40 min after 8 a.m. = 10.40 a.m.

Time that Mr Lim left the house = 10.40 a.m.

Time that Mr Lim took from 10.40 a.m. to 3 p.m. to reach his destination = 4 h 20 min

1 min = ¹₆₀ h
20 min = ²⁰₆₀ h = ¹₃ h
4 h 20 min = 4¹₃ h

Distance that Mr Lim drove
= 4¹₃ x 104
= 450²₃ km

Distance that Mrs Lim drove when Mr Lim reached
= 450²₃ - 22 
= 428²₃ km

Time that Mrs Lim took to travel from 8 a.m. to 3 p.m. = 7 h

Mrs Lim's average speed
= 428²₃ ÷ 7
= 61⁵₂₁ km/h

Answer(s): 61⁵₂₁ km/h