Mrs Quek left home at 7 a.m. and drove towards the city. 2⁵₁₂ hour later, Mr Quek left the house and drove at an average speed of 97 km/h towards the city. When Mr Quek reached his destination at 1 p.m., Mrs Quek was 24 km away from the city. Find Mrs Quek’s average speed in km/h. Express your answer in mixed number.
1 h = 60 min 
⁵₁₂ h = ⁵₁₂ x 60 = 25 min
2⁵₁₂ = 2 h 25 min

2 h 25 min after 7 a.m. = 9.25 a.m.

Time that Mr Quek left the house = 9.25 a.m.

Time that Mr Quek took from 9.25 a.m. to 1 p.m. to reach his destination = 3 h 35 min

1 min = ¹₆₀ h
35 min = ³⁵₆₀ h = ⁷₁₂ h
3 h 35 min = 3⁷₁₂ h

Distance that Mr Quek drove
= 3⁷₁₂ x 97
= 347⁷₁₂ km

Distance that Mrs Quek drove when Mr Quek reached
= 347⁷₁₂ - 24 
= 323⁷₁₂ km

Time that Mrs Quek took to travel from 7 a.m. to 1 p.m. = 6 h

Mrs Quek's average speed
= 323⁷₁₂ ÷ 6
= 53⁶⁷₇₂ km/h

Answer(s): 53⁶⁷₇₂ km/h