What are the least number of square tiles required to pave the floor of a room 15 m 17 cm long and 9 m 2 cm broad ?

In this type of questions, first we need to calculate the area of tiles. With we can get by obtaining the length of largest tile.
Length of largest tile can be obtained from HCF of length and breadth.
So lets solve this,
Length of largest tile = HCF of (1517 cm and 902 cm)
= 41 cm
Required number of tiles =
                                       $$\begin{gathered} \frac{Area of floor}{Area if tile} \\ =\left(\frac{1517\times 902}{41\times 41}\right) \\ =814 \end{gathered}$$