Mrs Choy left home at 9 a.m. and drove towards the city. 1¹₂ hour later, Mr Choy left the house and drove at an average speed of 95 km/h towards the city. When Mr Choy reached his destination at 3 p.m., Mrs Choy was 11 km away from the city. Find Mrs Choy’s average speed in km/h. Express your answer in mixed number.
1 h = 60 min 
¹₂ h = ¹₂ x 60 = 30 min
1¹₂ = 1 h 30 min

1 h 30 min after 9 a.m. = 10.30 a.m.

Time that Mr Choy left the house = 10.30 a.m.

Time that Mr Choy took from 10.30 a.m. to 3 p.m. to reach his destination = 4 h 30 min

1 min = ¹₆₀ h
30 min = ³⁰₆₀ h = ¹₂ h
4 h 30 min = 4¹₂ h

Distance that Mr Choy drove
= 4¹₂ x 95
= 427¹₂ km

Distance that Mrs Choy drove when Mr Choy reached
= 427¹₂ - 11 
= 416¹₂ km

Time that Mrs Choy took to travel from 9 a.m. to 3 p.m. = 6 h

Mrs Choy's average speed
= 416¹₂ ÷ 6
= 69⁵₁₂ km/h

Answer(s): 69⁵₁₂ km/h