Volume of cistern = 150 × 120 × 110

= 1980000 cm^{3}

Volume to be filled in cistern = 1980000 − 129600 = 1850400 cm^{3}

Let n numbers of porous bricks were placed in the cistern.

Volume of n bricks = n × 22.5 × 7.5 × 6.5

= 1096.875n

As each brick absorbs one-seventeenth of its volume, therefore, volume absorbed by these bricks = n/17(1096.875)

Therefore, 1792 bricks were placed in the cistern.