Mrs Goh left home at 7 a.m. and drove towards the city. 2¹₂ hour later, Mr Goh left the house and drove at an average speed of 96 km/h towards the city. When Mr Goh reached his destination at 2 p.m., Mrs Goh was 15 km away from the city. Find Mrs Goh’s average speed in km/h. Express your answer in mixed number.
1 h = 60 min 
¹₂ h = ¹₂ x 60 = 30 min
2¹₂ = 2 h 30 min

2 h 30 min after 7 a.m. = 9.30 a.m.

Time that Mr Goh left the house = 9.30 a.m.

Time that Mr Goh took from 9.30 a.m. to 2 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 Goh drove
= 4¹₂ x 96
= 432 km

Distance that Mrs Goh drove when Mr Goh reached
= 432 - 15 
= 417 km

Time that Mrs Goh took to travel from 7 a.m. to 2 p.m. = 7 h

Mrs Goh's average speed
= 417 ÷ 7
= 59⁴₇ km/h

Answer(s): 59⁴₇ km/h