Mrs Choo left home at 10 a.m. and drove towards the city. 1²₃ hour later, Mr Choo left the house and drove at an average speed of 110 km/h towards the city. When Mr Choo reached his destination at 3 p.m., Mrs Choo was 25 km away from the city. Find Mrs Choo’s average speed in km/h. Express your answer in mixed number.
1 h = 60 min 
²₃ h = ²₃ x 60 = 40 min
1²₃ = 1 h 40 min

1 h 40 min after 10 a.m. = 11.40 a.m.

Time that Mr Choo left the house = 11.40 a.m.

Time that Mr Choo took from 11.40 a.m. to 3 p.m. to reach his destination = 3 h 20 min

1 min = ¹₆₀ h
20 min = ²⁰₆₀ h = ¹₃ h
3 h 20 min = 3¹₃ h

Distance that Mr Choo drove
= 3¹₃ x 110
= 366²₃ km

Distance that Mrs Choo drove when Mr Choo reached
= 366²₃ - 25 
= 341²₃ km

Time that Mrs Choo took to travel from 10 a.m. to 3 p.m. = 5 h

Mrs Choo's average speed
= 341²₃ ÷ 5
= 68¹₃ km/h

Answer(s): 68¹₃ km/h