Mrs Chye left home at 7 a.m. and drove towards the city. 1¹₆ hour later, Mr Chye left the house and drove at an average speed of 109 km/h towards the city. When Mr Chye reached his destination at 3 p.m., Mrs Chye was 12 km away from the city. Find Mrs Chye’s average speed in km/h. Express your answer in mixed number.
1 h = 60 min 
¹₆ h = ¹₆ x 60 = 10 min
1¹₆ = 1 h 10 min

1 h 10 min after 7 a.m. = 8.10 a.m.

Time that Mr Chye left the house = 8.10 a.m.

Time that Mr Chye took from 8.10 a.m. to 3 p.m. to reach his destination = 6 h 50 min

1 min = ¹₆₀ h
50 min = ⁵⁰₆₀ h = ⁵₆ h
6 h 50 min = 6⁵₆ h

Distance that Mr Chye drove
= 6⁵₆ x 109
= 744⁵₆ km

Distance that Mrs Chye drove when Mr Chye reached
= 744⁵₆ - 12 
= 732⁵₆ km

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

Mrs Chye's average speed
= 732⁵₆ ÷ 8
= 91²⁹₄₈ km/h

Answer(s): 91²⁹₄₈ km/h