Mrs Kok left home at 9 a.m. and drove towards the city. 1¹₆ hour later, Mr Kok left the house and drove at an average speed of 85 km/h towards the city. When Mr Kok reached his destination at 3 p.m., Mrs Kok was 11 km away from the city. Find Mrs Kok’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 9 a.m. = 10.10 a.m.

Time that Mr Kok left the house = 10.10 a.m.

Time that Mr Kok took from 10.10 a.m. to 3 p.m. to reach his destination = 4 h 50 min

1 min = ¹₆₀ h
50 min = ⁵⁰₆₀ h = ⁵₆ h
4 h 50 min = 4⁵₆ h

Distance that Mr Kok drove
= 4⁵₆ x 85
= 410⁵₆ km

Distance that Mrs Kok drove when Mr Kok reached
= 410⁵₆ - 11 
= 399⁵₆ km

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

Mrs Kok's average speed
= 399⁵₆ ÷ 6
= 66²³₃₆ km/h

Answer(s): 66²³₃₆ km/h