Mrs Chye left home at 9 a.m. and drove towards the city. 1⁵₆ hour later, Mr Chye left the house and drove at an average speed of 85 km/h towards the city. When Mr Chye reached his destination at 2 p.m., Mrs Chye was 14 km away from the city. Find Mrs Chye’s average speed in km/h. Express your answer in mixed number.
1 h = 60 min 
⁵₆ h = ⁵₆ x 60 = 50 min
1⁵₆ = 1 h 50 min

1 h 50 min after 9 a.m. = 10.50 a.m.

Time that Mr Chye left the house = 10.50 a.m.

Time that Mr Chye took from 10.50 a.m. to 2 p.m. to reach his destination = 3 h 10 min

1 min = ¹₆₀ h
10 min = ¹⁰₆₀ h = ¹₆ h
3 h 10 min = 3¹₆ h

Distance that Mr Chye drove
= 3¹₆ x 85
= 269¹₆ km

Distance that Mrs Chye drove when Mr Chye reached
= 269¹₆ - 14 
= 255¹₆ km

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

Mrs Chye's average speed
= 255¹₆ ÷ 5
= 51¹₃₀ km/h

Answer(s): 51¹₃₀ km/h