Mrs Gan left home at 9 a.m. and drove towards the city. 1¹₃ hour later, Mr Gan left the house and drove at an average speed of 102 km/h towards the city. When Mr Gan reached his destination at 2 p.m., Mrs Gan was 28 km away from the city. Find Mrs Gan’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 Gan left the house = 10.20 a.m.

Time that Mr Gan took from 10.20 a.m. to 2 p.m. to reach his destination = 3 h 40 min

1 min = ¹₆₀ h
40 min = ⁴⁰₆₀ h = ²₃ h
3 h 40 min = 3²₃ h

Distance that Mr Gan drove
= 3²₃ x 102
= 374 km

Distance that Mrs Gan drove when Mr Gan reached
= 374 - 28 
= 346 km

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

Mrs Gan's average speed
= 346 ÷ 5
= 69¹₅ km/h

Answer(s): 69¹₅ km/h