A rectangular plot measuring 90 metres by 50 metres is to be enclosed by wire fencing. If the poles of the fence are kept 10 metres apart, how many poles will be needed ?  Answers: A) 28 B) 56 C) 57 D) 58 E) none of these

Rationale: "solution perimeter of the plot = 2 ( 90 + 50 ) = 280 m . ∴ number of poles = [ 280 / 10 ] = 28 m answer a"
Answer: A