Mrs Yee left home at 9 a.m. and drove towards the city. 1¹₆ hour later, Mr Yee left the house and drove at an average speed of 102 km/h towards the city. When Mr Yee reached his destination at 3 p.m., Mrs Yee was 30 km away from the city. Find Mrs Yee’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 Yee left the house = 10.10 a.m.

Time that Mr Yee 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 Yee drove
= 4⁵₆ x 102
= 493 km

Distance that Mrs Yee drove when Mr Yee reached
= 493 - 30 
= 463 km

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

Mrs Yee's average speed
= 463 ÷ 6
= 77¹₆ km/h

Answer(s): 77¹₆ km/h