John goes to his office by car at a speed of 40kmph and reaches 8 minutes earlier. If he goes at a speed of 30kmph , he reaches 4mins late. What is the distance from his house to office?  Select.
A) 18 km
B) 20 km
C) 22 km
D) 24 km
E) 30 km

Rationale: let his office time be 10 a . m . he reaches office at 8 minutes earlier when he travels at 40 kmph = > he reaches at 9 : 52 a . m he reaches his office 4 minutes late when travels at 30 kmph speed = > he reaches at 10.04 a . m the time difference is ( 10.04 – 9.52 ) = 12 minutes let the distance be d and time = distance speed t 1 – t 2 = 12 minutes = 12 / 60 hours = 1 / 5 hours d / 30 – d / 40 = 1 / 5 ( 4 d - 3 d ) / 120 = 1 / 5 d = 24 km
Answer: D