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Question:

A rectangular pool 20 metres wide and 60 metres long is surrounded by a walkway of uniform width. If the total area of the walkway is 516 square metres, how wide, in metres, is the walkway?

Explanation:

Suppose the width of the walkway is x metres.

∴ Area of walkway = 516 = (60 + 2x) × (20 + 2x) – 60 × 20

516 = 1200 + 120x + 40x + 4x² – 1200

516 = 4x² + 160x

x² + 40x – 129 = 0

(x + 43)(x – 3) = 0

x = 3 or x = − 43

∵ Negative value of width is not possible.

∴ x = 3

Hence, option (c).