Mrs Long left home at 8 a.m. and drove towards the city. 1⁵₆ hour later, Mr Long left the house and drove at an average speed of 89 km/h towards the city. When Mr Long reached his destination at 3 p.m., Mrs Long was 25 km away from the city. Find Mrs Long’s average speed in km/h. Express your answer in mixed number.
1 h = 60 min 
⁵₆ h = ⁵₆ x 60 = 50 min
1⁵₆ = 1 h 50 min

1 h 50 min after 8 a.m. = 9.50 a.m.

Time that Mr Long left the house = 9.50 a.m.

Time that Mr Long took from 9.50 a.m. to 3 p.m. to reach his destination = 5 h 10 min

1 min = ¹₆₀ h
10 min = ¹⁰₆₀ h = ¹₆ h
5 h 10 min = 5¹₆ h

Distance that Mr Long drove
= 5¹₆ x 89
= 459⁵₆ km

Distance that Mrs Long drove when Mr Long reached
= 459⁵₆ - 25 
= 434⁵₆ km

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

Mrs Long's average speed
= 434⁵₆ ÷ 7
= 62⁵₄₂ km/h

Answer(s): 62⁵₄₂ km/h