Mrs Sher left home at 9 a.m. and drove towards the city. 1⁷₁₂ hour later, Mr Sher left the house and drove at an average speed of 89 km/h towards the city. When Mr Sher reached his destination at 3 p.m., Mrs Sher was 19 km away from the city. Find Mrs Sher’s average speed in km/h. Express your answer in mixed number.
1 h = 60 min 
⁷₁₂ h = ⁷₁₂ x 60 = 35 min
1⁷₁₂ = 1 h 35 min

1 h 35 min after 9 a.m. = 10.35 a.m.

Time that Mr Sher left the house = 10.35 a.m.

Time that Mr Sher took from 10.35 a.m. to 3 p.m. to reach his destination = 4 h 25 min

1 min = ¹₆₀ h
25 min = ²⁵₆₀ h = ⁵₁₂ h
4 h 25 min = 4⁵₁₂ h

Distance that Mr Sher drove
= 4⁵₁₂ x 89
= 393¹₁₂ km

Distance that Mrs Sher drove when Mr Sher reached
= 393¹₁₂ - 19 
= 374¹₁₂ km

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

Mrs Sher's average speed
= 374¹₁₂ ÷ 6
= 62²⁵₇₂ km/h

Answer(s): 62²⁵₇₂ km/h