Mrs Chew left home at 9 a.m. and drove towards the city. 1⁷₁₂ hour later, Mr Chew left the house and drove at an average speed of 95 km/h towards the city. When Mr Chew reached his destination at 2 p.m., Mrs Chew was 19 km away from the city. Find Mrs Chew’s average speed in km/h. Express your answer in mixed number.
1 h = 60 min 
⁷₁₂ h = ⁷₁₂ x 60 = 35 min
1⁷₁₂ = 1 h 35 min

1 h 35 min after 9 a.m. = 10.35 a.m.

Time that Mr Chew left the house = 10.35 a.m.

Time that Mr Chew took from 10.35 a.m. to 2 p.m. to reach his destination = 3 h 25 min

1 min = ¹₆₀ h
25 min = ²⁵₆₀ h = ⁵₁₂ h
3 h 25 min = 3⁵₁₂ h

Distance that Mr Chew drove
= 3⁵₁₂ x 95
= 324⁷₁₂ km

Distance that Mrs Chew drove when Mr Chew reached
= 324⁷₁₂ - 19 
= 305⁷₁₂ km

Time that Mrs Chew took to travel from 9 a.m. to 2 p.m. = 5 h

Mrs Chew's average speed
= 305⁷₁₂ ÷ 5
= 61⁷₆₀ km/h

Answer(s): 61⁷₆₀ km/h