Mrs Long left home at 9 a.m. and drove towards the city. 2¹₃ hour later, Mr Long left the house and drove at an average speed of 110 km/h towards the city. When Mr Long reached his destination at 3 p.m., Mrs Long was 28 km away from the city. Find Mrs Long’s average speed in km/h. Express your answer in mixed number.
1 h = 60 min 
¹₃ h = ¹₃ x 60 = 20 min
2¹₃ = 2 h 20 min

2 h 20 min after 9 a.m. = 11.20 a.m.

Time that Mr Long left the house = 11.20 a.m.

Time that Mr Long took from 11.20 a.m. to 3 p.m. to reach his destination = 3 h 40 min

1 min = ¹₆₀ h
40 min = ⁴⁰₆₀ h = ²₃ h
3 h 40 min = 3²₃ h

Distance that Mr Long drove
= 3²₃ x 110
= 403¹₃ km

Distance that Mrs Long drove when Mr Long reached
= 403¹₃ - 28 
= 375¹₃ km

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

Mrs Long's average speed
= 375¹₃ ÷ 6
= 62⁵₉ km/h

Answer(s): 62⁵₉ km/h