Mrs Seah left home at 8 a.m. and drove towards the city. 2²₃ hour later, Mr Seah left the house and drove at an average speed of 94 km/h towards the city. When Mr Seah reached his destination at 3 p.m., Mrs Seah was 20 km away from the city. Find Mrs Seah’s average speed in km/h. Express your answer in mixed number.
1 h = 60 min 
²₃ h = ²₃ x 60 = 40 min
2²₃ = 2 h 40 min

2 h 40 min after 8 a.m. = 10.40 a.m.

Time that Mr Seah left the house = 10.40 a.m.

Time that Mr Seah took from 10.40 a.m. to 3 p.m. to reach his destination = 4 h 20 min

1 min = ¹₆₀ h
20 min = ²⁰₆₀ h = ¹₃ h
4 h 20 min = 4¹₃ h

Distance that Mr Seah drove
= 4¹₃ x 94
= 407¹₃ km

Distance that Mrs Seah drove when Mr Seah reached
= 407¹₃ - 20 
= 387¹₃ km

Time that Mrs Seah took to travel from 8 a.m. to 3 p.m. = 7 h

Mrs Seah's average speed
= 387¹₃ ÷ 7
= 55¹₃ km/h

Answer(s): 55¹₃ km/h