Mrs Yang left home at 7 a.m. and drove towards the city. 1³₄ hour later, Mr Yang left the house and drove at an average speed of 92 km/h towards the city. When Mr Yang reached his destination at 2 p.m., Mrs Yang was 27 km away from the city. Find Mrs Yang’s average speed in km/h. Express your answer in mixed number.
1 h = 60 min 
³₄ h = ³₄ x 60 = 45 min
1³₄ = 1 h 45 min

1 h 45 min after 7 a.m. = 8.45 a.m.

Time that Mr Yang left the house = 8.45 a.m.

Time that Mr Yang took from 8.45 a.m. to 2 p.m. to reach his destination = 5 h 15 min

1 min = ¹₆₀ h
15 min = ¹⁵₆₀ h = ¹₄ h
5 h 15 min = 5¹₄ h

Distance that Mr Yang drove
= 5¹₄ x 92
= 483 km

Distance that Mrs Yang drove when Mr Yang reached
= 483 - 27 
= 456 km

Time that Mrs Yang took to travel from 7 a.m. to 2 p.m. = 7 h

Mrs Yang's average speed
= 456 ÷ 7
= 65¹₇ km/h

Answer(s): 65¹₇ km/h