Estimating floor tiles for a hall

A rectangular hall measures \(31.8\text{ m}\) by \(19.6\text{ m}\). Square floor tiles have sides of \(49.5\text{ cm}\) and are sold in boxes of \(24\).

1. By rounding each length to \(1\) significant figure, estimate the number of tiles needed to cover the floor.[2]
2. Hence estimate the number of boxes needed.[1]
3. Assuming tiles can be cut and every offcut is used, calculate the least number of whole tiles needed and the number of boxes.[2]
4. Explain why the estimate in part (a) is smaller than the answer in part (c), and give one reason why a builder would still order more boxes than part (c) suggests.[2]