A rectangular plot measuring 90 metres by 60 metres is to be enclosed by wire fencing. If the poles of the fence are kept 5 metres apart, how many poles will be needed ?  Select the correct option.
A) 55  B) 56  C) 60  D) 58  E) none of these

Rationale: "solution perimeter of the plot = 2 ( 90 + 60 ) = 300 m . ∴ number of poles = [ 300 / 5 ] = 60 m answer c"
Answer: C