question from real numbers

We are being asked about such square tiles which can cover the whole courtyard. Indirectly, they are asking us the largest possible number which can divide both 18m 72cm and 13m 20cm.

 

i.e. the HCF of 18m 72cm = 1872 cm and 13m 20cm= 1320 cm

 

HCF of these two will be 24 cm.

 

So you will use 24cm by 24 cm square tiles.

And there will be a total of (1870 * 1320)/ (24*24) = 78 *  55= 4290 tiles.