Mrs Teo left home at 10 a.m. and drove towards the city. 1¹₂ hour later, Mr Teo left the house and drove at an average speed of 88 km/h towards the city. When Mr Teo reached his destination at 2 p.m., Mrs Teo was 15 km away from the city. Find Mrs Teo’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 Teo left the house = 11.30 a.m.

Time that Mr Teo 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 Teo drove
= 2¹₂ x 88
= 220 km

Distance that Mrs Teo drove when Mr Teo reached
= 220 - 15 
= 205 km

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

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

Answer(s): 51¹₄ km/h