Mrs Soh left home at 10 a.m. and drove towards the city. 1¹₂ hour later, Mr Soh left the house and drove at an average speed of 92 km/h towards the city. When Mr Soh reached his destination at 2 p.m., Mrs Soh was 25 km away from the city. Find Mrs Soh’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 10 a.m. = 11.30 a.m.

Time that Mr Soh left the house = 11.30 a.m.

Time that Mr Soh took from 11.30 a.m. to 2 p.m. to reach his destination = 2 h 30 min

1 min = ¹₆₀ h
30 min = ³⁰₆₀ h = ¹₂ h
2 h 30 min = 2¹₂ h

Distance that Mr Soh drove
= 2¹₂ x 92
= 230 km

Distance that Mrs Soh drove when Mr Soh reached
= 230 - 25 
= 205 km

Time that Mrs Soh took to travel from 10 a.m. to 2 p.m. = 4 h

Mrs Soh's average speed
= 205 ÷ 4
= 51¹₄ km/h

Answer(s): 51¹₄ km/h