A person crosses a 1440 m long street in 12 minutes. What is his speed in km per hour? Choices:
A) 4.1
B) 4.5
C) 4.8
D) 5.4
E) 7.2

Rationale: "speed = 1440 / ( 12 x 60 ) m / sec = 2 m / sec . converting m / sec to km / hr = 2 x ( 18 / 5 ) km / hr = 7.2 km / hr . answer : e"
Answer: E