Mrs Sher left home at 7 a.m. and drove towards the city. 3¹₃ hour later, Mr Sher left the house and drove at an average speed of 102 km/h towards the city. When Mr Sher reached his destination at 2 p.m., Mrs Sher was 20 km away from the city. Find Mrs Sher’s average speed in km/h. Express your answer in mixed number.
1 h = 60 min 
¹₃ h = ¹₃ x 60 = 20 min
3¹₃ = 3 h 20 min

3 h 20 min after 7 a.m. = 10.20 a.m.

Time that Mr Sher left the house = 10.20 a.m.

Time that Mr Sher took from 10.20 a.m. to 2 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 Sher drove
= 3²₃ x 102
= 374 km

Distance that Mrs Sher drove when Mr Sher reached
= 374 - 20 
= 354 km

Time that Mrs Sher took to travel from 7 a.m. to 2 p.m. = 7 h

Mrs Sher's average speed
= 354 ÷ 7
= 50⁴₇ km/h

Answer(s): 50⁴₇ km/h