The Landlord's Garden

The Story: Suresh owns a rectangular piece of land in Coimbatore that measures 60 metres long and 40 metres wide. He wants to create a garden path that runs diagonally across his property — from the top-left corner to the bottom-right corner. His gardener, Murugan, needs to know the exact length of this diagonal path so he can buy the right amount of paving stones. Each paving stone is 1 metre long. 'Just measure it,' Suresh says. 'I cannot,' Murugan says. 'The land is full of trees and I cannot walk in a straight line across it. But I know the two side lengths.' Suresh pulls out a scrap of paper. He sketches a rectangle and draws a diagonal line across it. '60 metres by 40 metres,' Suresh says. 'We can calculate the exact length without measuring it at all.' The Challenge: What is the exact length of the diagonal path across Suresh's 60 x 40 metre rectangular land? How many paving stones does Murugan need to buy, and why might he need to buy one extra?