A living room, if the area is 9 square decimeters of square paving need 144, if the area is 16 square decimeters of paving, how many?

A living room, if the area is 9 square decimeters of square paving need 144, if the area is 16 square decimeters of paving, how many?

Because sitting room area is changeless, so, the number that need and square brick area become inverse proportion
Set X blocks
16x=9×144
x=9×144÷16
x=81
A: it costs 81 yuan