Length of a tile = 15m 17m = 1517 cm
Breadth of a tile = 9m 2m = 902 cm
Required number of tiles =( Area of ceiling)/ (Area of one tile ) …..(1)
Side of each tile = HCF (1517 and 902)
1517 = 37 x 41
902 = 22 x 41
HCF = 41
Area of one tile = (side)2 = 41 x 41
Equation (1) implies
Required number of tiles = (1517 x 902)/41×41 = 814