Mrs Hun left home at 9 a.m. and drove towards the city. 2⁷₁₂ hour later, Mr Hun left the house and drove at an average speed of 109 km/h towards the city. When Mr Hun reached his destination at 3 p.m., Mrs Hun was 24 km away from the city. Find Mrs Hun’s average speed in km/h. Express your answer in mixed number.
1 h = 60 min 
⁷₁₂ h = ⁷₁₂ x 60 = 35 min
2⁷₁₂ = 2 h 35 min

2 h 35 min after 9 a.m. = 11.35 a.m.

Time that Mr Hun left the house = 11.35 a.m.

Time that Mr Hun took from 11.35 a.m. to 3 p.m. to reach his destination = 3 h 25 min

1 min = ¹₆₀ h
25 min = ²⁵₆₀ h = ⁵₁₂ h
3 h 25 min = 3⁵₁₂ h

Distance that Mr Hun drove
= 3⁵₁₂ x 109
= 372⁵₁₂ km

Distance that Mrs Hun drove when Mr Hun reached
= 372⁵₁₂ - 24 
= 348⁵₁₂ km

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

Mrs Hun's average speed
= 348⁵₁₂ ÷ 6
= 58⁵₇₂ km/h

Answer(s): 58⁵₇₂ km/h