A boy is travelling from his home to school at 6km/hr and reached 7min late. Next day he travelled at 12km/hr and reached 8min early. Distance between home and school?
Choose the correct choice from the following choices:
A) 2 km
B) 3 km
C) 4 km
D) 5 km
E) 6 km

Rationale: "let the distance be x t 1 = x / 6 hr t 2 = x / 12 hr difference in time = 7 + 8 = 15 = 1 / 4 hr x / 6 - x / 12 = 1 / 4 x / 12 = 1 / 4 x = 3 km answer is b"
Answer: B