Mrs Sim left home at 8 a.m. and drove towards the city. 1¹₄ hour later, Mr Sim left the house and drove at an average speed of 88 km/h towards the city. When Mr Sim reached his destination at 1 p.m., Mrs Sim was 11 km away from the city. Find Mrs Sim’s average speed in km/h. Express your answer in mixed number.
1 h = 60 min 
¹₄ h = ¹₄ x 60 = 15 min
1¹₄ = 1 h 15 min

1 h 15 min after 8 a.m. = 9.15 a.m.

Time that Mr Sim left the house = 9.15 a.m.

Time that Mr Sim took from 9.15 a.m. to 1 p.m. to reach his destination = 3 h 45 min

1 min = ¹₆₀ h
45 min = ⁴⁵₆₀ h = ³₄ h
3 h 45 min = 3³₄ h

Distance that Mr Sim drove
= 3³₄ x 88
= 330 km

Distance that Mrs Sim drove when Mr Sim reached
= 330 - 11 
= 319 km

Time that Mrs Sim took to travel from 8 a.m. to 1 p.m. = 5 h

Mrs Sim's average speed
= 319 ÷ 5
= 63⁴₅ km/h

Answer(s): 63⁴₅ km/h