Mrs Neo left home at 7 a.m. and drove towards the city. 3³₄ hour later, Mr Neo left the house and drove at an average speed of 105 km/h towards the city. When Mr Neo reached his destination at 3 p.m., Mrs Neo was 11 km away from the city. Find Mrs Neo’s average speed in km/h. Express your answer in mixed number.
1 h = 60 min 
³₄ h = ³₄ x 60 = 45 min
3³₄ = 3 h 45 min

3 h 45 min after 7 a.m. = 10.45 a.m.

Time that Mr Neo left the house = 10.45 a.m.

Time that Mr Neo took from 10.45 a.m. to 3 p.m. to reach his destination = 4 h 15 min

1 min = ¹₆₀ h
15 min = ¹⁵₆₀ h = ¹₄ h
4 h 15 min = 4¹₄ h

Distance that Mr Neo drove
= 4¹₄ x 105
= 446¹₄ km

Distance that Mrs Neo drove when Mr Neo reached
= 446¹₄ - 11 
= 435¹₄ km

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

Mrs Neo's average speed
= 435¹₄ ÷ 8
= 54¹³₃₂ km/h

Answer(s): 54¹³₃₂ km/h