Mrs Teo left home at 9 a.m. and drove towards the city. 1¹₃ hour later, Mr Teo left the house and drove at an average speed of 99 km/h towards the city. When Mr Teo reached his destination at 3 p.m., Mrs Teo was 16 km away from the city. Find Mrs Teo’s average speed in km/h. Express your answer in mixed number.
1 h = 60 min 
¹₃ h = ¹₃ x 60 = 20 min
1¹₃ = 1 h 20 min

1 h 20 min after 9 a.m. = 10.20 a.m.

Time that Mr Teo left the house = 10.20 a.m.

Time that Mr Teo took from 10.20 a.m. to 3 p.m. to reach his destination = 4 h 40 min

1 min = ¹₆₀ h
40 min = ⁴⁰₆₀ h = ²₃ h
4 h 40 min = 4²₃ h

Distance that Mr Teo drove
= 4²₃ x 99
= 462 km

Distance that Mrs Teo drove when Mr Teo reached
= 462 - 16 
= 446 km

Time that Mrs Teo took to travel from 9 a.m. to 3 p.m. = 6 h

Mrs Teo's average speed
= 446 ÷ 6
= 74¹₃ km/h

Answer(s): 74¹₃ km/h